The five incurable actions

When a warrior strives and struggles in battle, their mind is already low, degraded, and misdirected as they think:
Yo so, gāmaṇi, yodhājīvo saṅgāme ussahati vāyamati, tassa taṁ cittaṁ pubbe gahitaṁ dukkaṭaṁ duppaṇihitaṁ:

‘May these sentient beings be killed, slaughtered, slain, destroyed, or annihilated!’

His foes kill him and finish him off, and when his body breaks up, after death, he’s reborn in the hell called ‘The Fallen’.
SN 42.3

From the sutta quote above, we see that the warrior who strives (ussahati) and struggles or exerts himself (vāyamati) in battle, is already deep in the low, degraded and misdirected mindset of killing.

Similarly, just having the fleeting thought of hurting the Buddha, killing an arahant, killing one's mother, killing one's father or causing a schism in the Buddha's sangha, is not sufficient to be considered an incurable action.

It's an incurable action only when one strives (ussahati) and struggles or exerts himself (vāyamati) to commit those heinous acts, regardless of whether he has actually been successful or not, just as in the case of the warrior in battle.

So, yes, even an unsuccessful intentional and deliberate attempt to perform these wicked acts would be incurable.

The OP asked in the comments to the effect of: What about Angulimala who killed many humans and attempted to kill the Buddha, but eventually became an arahant?

When Angulimala attempted to kill the Buddha, he did not know that it was the Buddha or an arahant. He only saw a monk walking alone along the road.

So he did not have the intention to kill the Buddha. He only had the intention to kill a monk.

It's just like the difference between intentionally killing an unknown woman who the killer did not know to be his mother, and intentionally killing his own mother knowingly. The latter carries more terrible consequences than the former.

Please read the story of Chakkhupala in the commentary of Dhammapada 1 and also the quote:

"Intention, I tell you, is kamma. Intending, one does kamma by way of body, speech, & intellect." - AN 6.63

Karma is based on intention in Buddhism. Karma is not a universal system of justice.

The sutta below clearly shows that merely thinking about hurting Ven. Sariputta did not cause karmic consequences for the yakkha.

However, intentionally striving and exerting himself to hurt Ven. Sariputta caused the yakkha to experience karmic consequences, even if Ven. Sariputta was not successfully hurt the way he intended him to be.

This shows that striving and exerting oneself results in karmic consequences, whether or not the intended action reached its intended outcome.

And on that occasion two yakkhas who were companions were flying from north to south on some business or other. They saw Ven. Sāriputta — his head newly shaven — sitting in the open air. Seeing him, the first yakkha said to the second, "I'm inspired to give this contemplative a blow on the head."

When this was said, the second yakkha said to the first, "Enough of that, my good friend. Don't lay a hand on the contemplative. He's an outstanding contemplative, of great power & great might."

A second time, the first yakkha said to the second, "I'm inspired to give this contemplative a blow on the head."

A second time, the second yakkha said to the first, "Enough of that, my good friend. Don't lay a hand on the contemplative. He's an outstanding contemplative, of great power & great might."

A third time, the first yakkha said to the second, "I'm inspired to give this contemplative a blow on the head."

A third time, the second yakkha said to the first, "Enough of that, my good friend. Don't lay a hand on the contemplative. He's an outstanding contemplative, of great power & great might."

Then the first yakkha, ignoring the second yakkha, gave Ven. Sāriputta a blow on the head. And with that blow he might have knocked over an elephant seven or eight cubits tall, or split a great rocky crag. But right there the yakkha — yelling, "I'm burning!" — fell into the Great Hell.

Now, Ven. Moggallāna — with his divine eye, pure and surpassing the human — saw the yakkha give Ven. Sāriputta a blow on the head. Seeing this, he went to Ven. Sāriputta and, on arrival, said to him, "I hope you are well, friend Sāriputta. I hope you are comfortable. I hope you are feeling no pain."

"I am well, friend Moggallāna. I am comfortable. But I do have a slight headache."

"How amazing, friend Sāriputta! How astounding! How great your power & might! Just now a yakkha gave you a blow on the head. So great was that blow that he might have knocked over an elephant seven or eight cubits tall, or split a great rocky crag. But all you say is this: 'I am well, friend Moggallāna. I am comfortable. But I do have a slight headache'!"

"How amazing, friend Moggallāna! How astounding! How great your power & might! Where you saw a yakkha just now, I didn't even see a dust devil!"
Ud 4.4

Usually, one who fails in following his intention, based on wrong view, sees himself right after his fail in hell. Think on crazy people after destructive things now hold back in performing them material. Likewise a person who desire to hold on wrong view, but fails to get approve. This, reflected, might release not only from the target of the adept here but also from it's underlying similarity. Just look right here, good householder.

Kamma has three/four ways of progress, by body, by signs, speech in order a deed, by rejoice and approve. Destruction and harm in one of those ways has it's hellish results. Not having a gun or not reaching out being handicapped doesn't prevent from kamma. Otherwise education camps and prisons would be good ways to make ways of people generally better.

Btw. holding on grave wrong views is the sixth, a 'problem' most modern people have, incapable to get the Dhammas track.

So take care when thinking gaming is just a game and watching movies and news just entertainment.

Since going to hell is a dangerous experiment to conduct, let's focus instead on what we can all verify. In particular, note that action conditioned by ignorance in body, speech or mind cause pleasure and pain to arise.

AN4.171:1.1: “Mendicants, as long as there’s a body, the intention that gives rise to bodily action causes pleasure and pain to arise in oneself.
AN4.171:1.2: As long as there’s a voice, the intention that gives rise to verbal action causes pleasure and pain to arise in oneself.
AN4.171:1.3: As long as there’s a mind, the intention that gives rise to mental action causes pleasure and pain to arise in oneself. But these only apply when conditioned by ignorance.

Killing is a bodily action. Thinking about killing is a mental action. Therefore, just thinking about killing a parent will cause pain and suffering. The difference between killing and thinking about killing a parent is that one cannot unkill a parent. But one can relinquish the thought of killing a parent--even if that thought arises again. And in relinquishing the thought of killing, one can also gradually relinquish ignorance. In this way, thinking about killing a parent is like standing on the edge of hell, leaning forward.

For those who fall into hell there is slim hope.

MN50:21.1: Then Māra Dūsī took possession of a certain boy, picked up a rock, and hit Vidhura on the head, cracking it open.
MN50:21.2: Then Vidhura, with blood pouring from his cracked skull, still followed behind the Buddha Kakusandha.
MN50:21.3: Then the Buddha Kakusandha turned his whole body, the way that elephants do, to look back, saying,
MN50:21.4: ‘This Māra Dūsī knows no bounds.’
MN50:21.5: And with that look Māra Dūsī fell from that place and was reborn in the Great Hell.

Once in Hell, the pain lasts for a very long time as one struggles to emerge from Hell. There is no "parole". There is no doctor nor cure (atekicchā). A sentence to Hell must be served in its entirety.

MN50:23.2: For ten thousand years I roasted in the annex of that Great Hell, experiencing the pain called ‘emergence’.

Eventually, Dūsī served his sentence and was released. And eventually, Dūsī became known as Moggallāna, one of the Gautama Buddha's chief disciples.

So rather than jump into Hell for ten thousand years, perhaps it is better to pull back from the precipice to Hell. Perhaps it is best to restrain and relinquish unskillful thoughts.