Anakin isn't looking for a fight, but he's absolutely never in his life avoided one unless he had to. But there's a lot of fighting now, with Dominants particularly under attack. There's some small part of Anakin that doesn't feel that bad about it, because these are the people that own other people. Of course he's aware that LIES participants generally aren't like that, they didn't choose their fate. But he can't help that little dark part of himself.

He can help how he reacts to those thoughts, though. He's self-aware enough to do that, at least for the time being. So he's decided that if he can help, then he will. People don't deserve to be attacked for nothing, regardless of Anakin's knee-jerk thoughts about it.

He's not drawn to Luke's fight because Luke needs help, of course. He's drawn by the Force, the recognition of another person who is very strong in it. If there's some hint of familiarity, he can't track it. He doesn't know, after all. He knows the future, or thinks he does, but he has no idea about Luke or Leia or that Kylo is his blood relation. He still thinks he dies, but even if that were true (and it's sort of true), Padmé would already be pregnant when that confrontation on Mustafar happens. No one has told him about those particular details, probably for the better.

He gets to this alleyway fight in time to catch just one person, running in surprise from Luke's attack. Anakin barely needs to do anything to take that one out. He doesn't even look at them. He doesn't kill them, though he considers it. It would be a poor introduction, and besides, he's trying to be a better person. He really is.

"That's quite a fighting style you have there," he says, looking up at Luke from the unconscious body lying in front of him.