Did the Buddha say anything about bullying?

The Buddha taught kids to not bully and harm a snake. And that applies to all in general.

I have heard that on one occasion the Blessed One was staying near Sāvatthī at Jeta's Grove, Anāthapiṇḍika's monastery. And on that occasion, a large number of boys on the road between Sāvatthī & Jeta's Grove were hitting a snake with a stick. Then early in the morning the Blessed One adjusted his under robe and — carrying his bowl & robes — went into Sāvatthī for alms. He saw the large number of boys on the road between Sāvatthī & Jeta's Grove hitting the snake with a stick.

Then, on realizing the significance of that, the Blessed One on that occasion exclaimed:

Whoever hits with a stick
beings desiring ease,
when he himself is looking for ease,
will meet with no ease after death.

Whoever doesn't hit with a stick
beings desiring ease,
when he himself is looking for ease,
will meet with ease after death.
Ud 2.3

The same thing in Dhammapada 131 - 132.

There is this story about a bhikkhu killing a swan in the commentary to dhp393;

Once there was a bhikkhu who was very skilful in throwing stones; he could even hit fast-moving objects without fail. One day, while sitting with another bhikkhu after having their bath in the Aciravati River, he saw two swans flying at some distance. He told his friend that he would get one of the swans by throwing a stone at it. At that instant, the swan, hearing voices, turned its neck and the bhikkhu threw a pebble at the bird. The pebble went through one eye and came out of the other eye of the bird. The bird cried out in pain and agony and dropped dead at the feet of the young bhikkhu.

Other bhikkhus seeing the incident took the young bhikkhu to the Buddha. The Buddha reprimanded him and said, "My son, why have you killed this bird? Why especially you, a member of my Order, who should be practising loving-kindness to all beings and who should be striving ardently for liberation from the round of rebirths? Even during the period outside the Teaching, the wise practised morality and observed the precepts. A bhikkhu must have control over his hands, his feet and his tongue." https://www.tipitaka.net/tipitaka/dhp/verseload.php?verse=362

I recall hearing or reading another story about a person from a low caste being abused, iirc people were throwing stones at a guy for no particular reason other than him being from the bad caste and the Tathagatha intervened by placing himself inbetween the abusers and the abused. Unfortunely i can't remember the origin and couldn't find it. Perhaps someone else will post it, i guess it's also from the Dhp commentary.

Everybody, included outsider laymen and animals, must be effected by 10 Akusalakammapatha and 10 Kusalakamapatha. There are many explaination such as in DN 1,2:

"Abandoning false speech, he abstains from false speech. He speaks the truth, holds to the truth, is firm, reliable, no deceiver of the world. This, too, is part of his virtue.

"Abandoning divisive speech he abstains from divisive speech. What he has heard here he does not tell there to break those people apart from these people here. What he has heard there he does not tell here to break these people apart from those people there. Thus reconciling those who have broken apart or cementing those who are united, he loves concord, delights in concord, enjoys concord, speaks things that create concord. This, too, is part of his virtue.

"Abandoning abusive speech, he abstains from abusive speech. He speaks words that are soothing to the ear, that are affectionate, that go to the heart, that are polite, appealing and pleasing to people at large. This, too, is part of his virtue.

"Abandoning idle chatter, he abstains from idle chatter. He speaks in season, speaks what is factual, what is in accordance with the goal, the Dhamma, and the Vinaya. He speaks words worth treasuring, seasonable, reasonable, circumscribed, connected with the goal. This, too, is part of his virtue.

For the techniques in MN Araṇavibhaṅgasuttaṃ (I cut some part here, it is better to recite whole Sutta and find the word linking yourself every day a year. It's going to appear clearer and clearer):

It was said, do not tell secrets, do not express destruction of desires in the face. Why was it said so? There bhikkhus, if you know of some secret, which did not happen, is not true, not conducive to good, if possible do not tell that secret. If you know of some secret which happened, is true and is not conducive to good, train not to tell it. If you know of some secret which happened, is true and is conducive to good, know the right time to tell it. There, bhikkhus, if you know of some destruction of desires that did not happen, is not true, not conducive to good, if possible do not tell that destruction of desires in the face. If you know of some destruction of desires that happened, is true and is not conducive to good, train not to tell it. in the face. If you know of some destruction of desires that happened, is true and is conducive to good, know the right time to tell it. in the face. If it was said, do not tell secrets, do not express destruction of desires in the face, it was said on account of this.

It was said, do not express words hastily, speak leisurely. Why was it said so? Bhikkhus, the one speaking hastily, fatigues the body, disturbs the mind and voice, the throat gets sore, and the words not well enunciated, are not well understood. The one speaking leisurely, does not, fatigue the body, disturb the mind and voice, the throat does not get sore, and the well enunciated words, are well understood

If it was said do not express words hastily, speak leisurely. it was said on account of this.

It was said, do not insist for local expressions and do not over ride the popular usage. Why was it said so? Bhikkhus, how is there insistence for local expressions and how is the popular usage over ridden? Bhikkhus, in a certain state the bowl is known as Pātīti, in another Pattaṃ, in another Vitthaṃ, in another Sarāvaṇ, in another Dhāropan, in another Poṇan, and Pisīlan in yet another. By whatever name it is known in that and other state, it is taken as the highest truth and all else is not the truth. This is insisting for local expressions and over riding the popular usage. Bhikkhus, how is there no insistence for local expession and no over riding of popular usage? Bhikkhus, in a certain state the bowl is known as Pātīti, in another Pattaṃ, in another Vitthaṃ, in another Sarāvaṇ, in another Dhāropan, in another Poṇan, and Pisīlan in yet another. By whatever name it is known in that and other state, the venerable one knows, it is the bowl that is known, and thinks nothing more about it. Thus there is no insistence for local expession and no over riding of popular usage. If it was said, do not insist for local expressions and do not over ride the popular usage. it was said on account of this.

Therefore bhikkhus, ‘He that finds pleasantness in rebirth, yoked to low, vile, useless not noble pleasures, is with, unpleasantness, troubles, fever, lament and is in the wrong method’, this thing is with a refuge Therefore bhikkhus, ‘He that does not find pleasantness in rebirth, unyoked from low, vile, useless not noble pleasures is without, unpleasantness, troubles, fever, lament and is in the right method,’ this thing is without a refuge. Therefore bhikkhus, Yoked to the not noble useless torturing of the self, one is with, unpleasantness, troubles, fever, lament and is in the wrong method,’ this thing is with a refuge. Therefore bhikkhus, ‘Unyoked from the not noble useless torturing of the self, one is without, unpleasantness, troubles, fever, lament and is in the right method,’ this thing is without a refuge. Therefore bhikkhus, the Thus Gone One has realizedthe middle path, which is conducive to wisdom, peace, knowledge, enlightenment and extinction. it is without, unpleasantness, troubles, fever, lament and is in the right method. ‘this thing is without a refuge. Therefore bhikkhus, praising and blaming and not giving the Teaching. is with, unpleasantness, troubles, fever, lament and is in the wrong method’, this thing is with a refugeTherefore bhikkhus, without praising and blaming giving the Teaching. is without unpleasantness, troubles, fever, lament and is in theright method’, this thing is without a refuge. Therefore bhikkhus, sense pleasures, vile pleasures of the not noble ordinary man is with, unpleasantness, troubles, fever, lament and is in the wrong method,’ this thing is with a refuge. Therefore bhikkhus, non sensual pleasure, the pleasure of seclusion, appeas*m*nt and enlightenment. is without, unpleasantness, troubles, fever, lament and is in the right method. ‘this thing is without a refuge. Bhikkhus, that secret, which did not happen, is not true, not conducive to good, is with, unpleasantness, troubles, fever, lament and is in the wrong method’, this thing is with a refuge. Bhikkhus, that secret which happened, is true and is not conducive to good is with, unpleasantness, troubles, fever, lament and is in the wrong method’, this thing is with a refuge Bhikkhus, that secret which happened, is true and is conducive to good, is without, unpleasantness, troubles, fever, lament and is in the right method’, this thing is without a refuge There, bhikkhus, the destruction of desires that did not happen, is not true, not conducive to good, told in the face. is with, unpleasantness, troubles, fever, lament and is the wrong method’, this thing is with a refuge There, bhikkhus, the destruction of desires that happened, is true and is not conducive to good, told in the face. is with, unpleasantness, troubles, fever, lament is the wrong method’, this thing is with a refuge. There, bhikkhus, thedestruction of desires that happened, is true and is conducive to good, ṭold in the face. is without, unpleasantness, troubles, fever, lament and is the right method’, this thing is without a refuge. There, bhikkhus, insisting for local expressions and over riding the popular usage. is with, unpleasantness, troubles, fever, lament and is the wrong method’, this thing is with a refuge. There, bhikkhus, not insisting for local expressions and not over riding the popular usage. is without, unpleasantness, troubles, fever, lament and is the right method’, this thing is without a refuge.

Therefore, bhikkhus, we should train knowing the things with a refuge and without a refuge. The clansman Subhūti has fallen to the methd of things without a refuge.”