Say UTG fish limps and you raise 5BB's in CO with AK and flop 2 pair. Villain donks out for a minbet, how much do you raise him? Most of the time when we play against competent players they are betting the usual 3/4 line, and then we 3x their bet to build a pot which doesnt give them great odds, but doesnt completely blow them out of the water either. So what do you do when villains fire 2 streets OOP with a minbet and you have a set or the undeniable nuts or so, obviously 3x'ing their minbet into a 20BB pot isnt getting much value. But villain might get scared off if you raise him 3/4 pot to his minbet, making him have to call 75% more than he intended to.

Is half pot a good rule of thumb? Maybe 5x his bet? Or just keep stabbing as usual and hope he's dumb enough to call for whatever reason?

If you think you're ahead or have the nuts, you're obviously trying to build a big pot, so just pretend those min-donkbets are a check and keep raising them as usual.

Raising to 2/3 pot on both the flop and turn will allow for a psb all-in by the river. So if the player is ATMish enough, go for this line every time.