The DMG on page 274 has guidelines about damage per round for monsters of each Challenge Rating. However, most monsters deal that damage as a combination of multiple attacks (and sometimes other abilities like breath weapons).
Are there statistics of average damage per attack for published monsters by Challenge Rating, for the most damaging attack these monsters have? (just Monster Manual would be OK)
To adress the questions: for clarification
I currently have no specific problem I am trying to solve with this, I am just curious. I could see it being useful, for example to evaluate how much damage a feat would be that granted Uncanny Dodge would avoid.
I originally meant attacks with an attack roll (i.e. things that say attack, like a melee or ranged attack that has a to hit), not things like area damage spells or breath weapons. This typically would exclude damage sources that need to recharge (at least I am not aware of a normal attack roll one, that has a recharge).
I would include extra typed damage that is the direct result of the attack.
I'd exclude spells, summoning abilities and secondary non-damage effects that cause things like conditions.
I would consider attacks lowering the hit point maximum like normal damage attacks.
I'd consider legendary actions if one of them dealt a higher attack damage than the normal attack.
I'd ignore effects that deal damage when you hit the creature.
However, an answer that included breath weapons and other damage dealing attack forms, or for some reason made another call on these would be OK for me, als long as it explains what is or is not included.