None of those acts compare to bashing someones brains in with a baseball bat.

Here's a few that do

Rick hitting the machete in Gareth's head over and over after he was dead

Rick breaking Bob's (not our Bob's) back and casually telling him he should've stopped

Rick biting into a man's throat

Rick gutting a man

Negan bashing Glenn's head in is a whole other level of Wrong.

Not on it's own. It's the context of these situations that make them bad or good. The reason all those Rick moments I mentioned are forgivable are because of how he did it and why. Gareth died instantly, even if Rick did seem to gain some sense of pleasure by stabbing him over and over, Bob was killed by a gunshot even if he did suffer for a moment, he bit into Joe's throat because he was preventing him from saving his son, he gutted the man because he almost raped his son

Negan's reasons for killing Glenn and Abraham make sense on paper. Negan wants Rick to break and work for him, and he wants to punish them for all of his men who died. The problem is how he dragged it out. He could've gone full forced and killed them with Lucille quickly, he didn't have to taunt Rosita with Abraham's blood, and he didn't have to enjoy it and make jokes about it

The act on it's own is not the problem