Unwholesome thoughts at the time of death

OP: My question: so should we not reflect on the beauty of something? It's not a bad karma, right? So I thought it will just create attachment (that bounds us to samsara), but I didn't think it would lead to a rebirth in the lower realms?

Reflecting on the beauty of something is fine. It does not generate any bad karma. The problem arises when we generate covetousness or craving for this beautiful thing due to our own ignorance. That will generate non-virtuous karma that can lead to an unfortunate rebirth.

Here is an example of the Buddha reflecting on beauty in a completely faultless way:

“This bhikkhu shines with sublime beauty,
Having a mind utterly straight.
Detached is he, free from fetters,
Attained to Nibbāna by nonclinging.
He carries about his final body,
Having conquered Mara and his mount.”

SN 21.5

This is often hard to understand for newcomers to Buddhism. They can misunderstand thinking that the Buddha basically said we should no longer love people or that we should no longer appreciate beauty in the world. This isn't the case. In fact, it is the exact opposite.

It is only through giving up covetousness and craving that we can truly love others. Our craving and greed is actually the enemy of being able to see and appreciate the beauty in this world. Craving and greed create bias and reduce our ability to see the world and people for what is actual. Instead, craving and greed and bias act as filters that harm us from being able to truly love and truly see.

The Buddha taught in the four immeasurables that instead we are to train our minds to perfect the ability to love all sentient beings with absolutely no craving. We are taught to train our minds to love without bias and to generate immeasurable joy at the happiness of others.

The third liberation is indeed focused on beauty:

AN8.66:3.1: They’re focused only on beauty.
AN8.66:3.2: This is the third liberation.

However, the trap here is identification:

beauty of one's children

The Buddha himself spoke to his own son by name, not as "My son":

MN62:3.2: “Rāhula, you should truly see any kind of form at all—past, future, or present; internal or external; coarse or fine; inferior or superior; far or near: all form—with right understanding: ‘This is not mine, I am not this, this is not my self.’”

Seeing beauty in "mine" is covetousness.

MN8:12.10: ‘Others will be covetous, but here we will not be covetous.’

Letting go of covetousness, we find beauty everywhere. Seeing beauty everywhere is to let go of "mine". Seeing beauty everywhere leads to rejoicing.

AN8.66:4.1: Going totally beyond perceptions of form, with the ending of perceptions of impingement, not focusing on perceptions of diversity, aware that ‘space is infinite’, they enter and remain in the dimension of infinite space.
AN8.66:4.2: This is the fourth liberation.

Pa Auk Sayadaw's quoted statement does not appear to align with what is in the Pali suttas.

If we read the Pali suttas, which are supposed to be the teachings of the Lord Buddha, we will not read the Buddha always teaching laypeople if they think of their loved ones at the time of death they will be reborn in hell. In fact, the suttas teach people who are alive should make offerings to their departed loved ones, as follows:

I shall offer alms in honor of my departed relatives

Sigalovada Sutta

The Buddha taught higher teachings for monks & wise people and lower moral teachings for laypeople. The Buddha said in the Samajivina Sutta a husband & wife who share the Dhamma will remain united with each other in both the present & the future. Therefore, obviously the Buddha never taught proper moral love for a husband or wife leads to hell. Obviously if during dying a person thinks with a heart of metta (virtuous love), their mind will be born into a heavenly state.

The quote in the OP seems to be about "beauty" and "unwise attention", and the question is about "reflecting on the beauty of something".

Whereas, for example, the Blessed One in the sutta Dhammadhatu quoted (AN 4.55) was talking about their being "in tune, in conviction, virtue, generosity, and discernment" -- I think that's not the same as superficial attractiveness, isn't that so?

The one bit of advice I've read about "wholesome thought at time of death is quoted here:

The Vinita-vatthu to Pr 4 contains a number of stories in which bhikkhus comfort a dying bhikkhu by asking him to reflect on what he has attained through the practice, which was apparently a common way of encouraging a dying bhikkhu to focus his thoughts on the best object possible.

And so for example, quoting from AN 4.55 again, this seems to me an example of "reflecting on an attainment", and not only "reflecting on the beauty":

Lord, ever since Nakula's mother as a young girl was brought to me [to be my wife] when I was just a young boy, I am not conscious of being unfaithful to her even in mind, much less in body. We want to see one another not only in the present life but also in the life to come.

It's perhaps an example of skillful virtue -- of evil action (being unfaithful) that wasn't done.

I see no contradiction -- one is saying that recollection of virtue is associated with "the world of the Devas", and the other that a habit of unwise attention on beauty makes wise attention at death more difficult.

There are two topics in your question.

One is what is considered as bad kamma in Buddhism. Another is how kamma influence where you would be reborn in Buddhism doctrine.

For the first part, to the non-monk people, if you follow the "path of the ten good actions" (daśa-kuśala-kammapatha), it is considered as good kamma in Buddhism. The opposite actions would be considered as bad kamma in Buddhism.

So the question would be to reflect on the beauty of something violates the "path of the ten good actions"?

You can see the introduction of the "path of the ten good actions" here.

https://en.wikipedia.org/wiki/Buddhist_ethics#Ten_wholesome_actions

The relative part is the first mental actions, "It’s when someone is content. They don’t covet the wealth and belongings of others".

So only if you covet the beauty of others, and want to possess it, it would be considered as bad kamma in Buddhism.

For the second part, it involves what and how "kamma factors" influence where you would be reborn.

There are four kinds of such "kamma factors":

1. weighty kamma (garu-kamma)
2. habitual kamma (bahula/acinnaka kamma)
3. death proximate kamma (asanna kamma)
4. stored up kamma (katatta kamma)

You can see the introduction here.

https://www.reddit.com/r/Buddhism/comments/1it0qr/the_mind_at_the_time_of_death/

Generally, "habitual kamma" should be the more important factor than "death proximate kamma". Because your habitual actions in everyday life would infect your thoughts of the mind when you near death (or other difficult occasions).

Although, it seems to me that in Theravada Buddhism, it is more popular or common to stress "death proximate kamma".

By the way, I would be caution to interpret or regard "the words of someone's translated works" word by word.

Pa Auk Sayadaw's works are Burmese originally. Beside, there might be cultural factors to play a role on the expressions used by different countries/cultural communities.

the key word is 'habitually looked' meaning one develops a strong habit. these stain the mind almost as though taking possession or control of it. prior to that is the unskillful perception arising from greed and delusions. prior to that is normal observation of beauty which is fine here but can easily become deluded. that is the way most of us practice, we jump into deluded activity and if we are intelligent we quickly see what should be taken up and what should be given up. whatever faulty activity we engage in we must always strive never to lose the protection of loving kindness and compassion or else all our efforts will amount to nothing

Ven. Pa Auk Sayadaw explains here that clinging leads to suffering, and in this case, this includes clinging to family members, clinging to their beauty, clinging to the beauty of possessions etc.

Being worried or concerned or obsessed about one's family members or their health, wealth, looks, possessions, career, future etc. are different expressions of clinging. The beauty of possessions is also impermanent.

This can be seen in SN 55.54 below.

The idea is to accept that one's own health and life, and one's family members and their health, wealth, possessions, looks, career, future etc. are all impermanent.

How is this related to karma? Well, clinging and craving leads to the three poisons of greed, aversion and delusion. The three poisons will lead to committing bad karma.

For e.g. I like the beauty of my plants, but my neighbour damages it, leading to my hurting or insulting him. I would have aversive emotions towards my neighbour because he disrupted my greedy emotions towards the beauty of my plants. These aversive emotions are suffering. Then this leads to the delusional mental state of rage and anger, leading to the bad karma of somehow taking revenge on my neighbour. Bad karma of harming my neighbour will somehow cause me further suffering in future.

So starting from craving and clinging, this will eventually lead to suffering.

Mahānāma the Sakyan heard about this. Then he went up to the Buddha, bowed, sat down to one side, and told him that he had heard that the Buddha was leaving. He added, “Sir, I haven’t heard and learned it in the presence of the Buddha how a wise lay follower should advise another wise lay follower who is sick, suffering, gravely ill.”

“Mahānāma, a wise lay follower should put at ease another wise lay follower who is sick, suffering, gravely ill with four consolations. ‘Be at ease, sir. You have experiential confidence in the Buddha … the teaching … the Saṅgha … And you have the ethical conduct loved by the noble ones … leading to immersion.’

When a wise lay follower has put at ease another wise lay follower who is sick, suffering, gravely ill with these four consolations, they should say: ‘Are you concerned for your mother and father?’ If they reply, ‘I am,’ they should say: ‘But sir, it’s your nature to die. Whether or not you are concerned for your mother and father, you will die anyway. It would be good to give up concern for your mother and father.’

If they reply, ‘I have given up concern for my mother and father,’ they should say: ‘But are you concerned for your partners and children?’ If they reply, ‘I am,’ they should say: ‘But sir, it’s your nature to die. Whether or not you are concerned for your partners and children, you will die anyway. It would be good to give up concern for your partners and children.’

If they reply, ‘I have given up concern for my partners and children,’ they should say: ‘But are you concerned for the five kinds of human sensual stimulation?’ If they reply, ‘I am,’ they should say: ‘Good sir, heavenly sensual pleasures are better than human sensual pleasures. It would be good to turn your mind away from human sensual pleasures and fix it on the gods of the Four Great Kings.’

If they reply, ‘I have done so,’ they should say: ‘Good sir, the gods of the Thirty-Three are better than the gods of the Four Great Kings …

Good sir, the gods of Yama … the Joyful Gods … the Gods Who Love to Create … the Gods Who Control the Creations of Others … the Gods of the Brahmā realm are better than the Gods Who Control the Creations of Others. It would be good to turn your mind away from the Gods Who Control the Creations of Others and fix it on the Gods of the Brahmā realm.’ If they reply, ‘I have done so,’ they should say: ‘Good sir, the Brahmā realm is impermanent, not lasting, and included within identity. It would be good to turn your mind away from the Brahmā realm and apply it to the cessation of identity.’

If they reply, ‘I have done so,’ then there is no difference between a lay follower whose mind is freed in this way and a mendicant whose mind is freed from defilements; that is, between the freedom of one and the other.”
SN 55.54