GingerW

I imagine it was guilt over being responsible for his sister being killed.

He's hardwired to help people.....no matter what. If it weren't for the no matter what , he would not have risked the lives of 100 bystanders on the train or the people at his sister's memorial to catch the "bad guys." Which is exactly the same thing that Hart's group does. Except their no matter what isn't going to be something he always agrees with like letting Mejia live to get intel. As a spec ops operator he would be familiar with the concept of "for the greater good." He's likely carried out assassinations that have nothing to do with justice, but with sacrificing the few to save the many (people). If Hart's group didn't care about people, they would have shot to kill him and saved themselves the hassle instead of offering him a job.

I like it too. Not so much for the Bryan Mills character but the set up and the badass team members. I'm thinking Mills is a bit too emotional/hot headed and not so smart. A closed train compartment. 100 bystanders and he's going to take down an operative with a cup of coffee? And an unknown van with who knows how many shooters. Let's just have them take out the rest of his family.

This. I'm not sure if it is the ridiculous, unkempt stubble or the aged appearance of the actor, but to me the trailers were hilarious because the sister looked young enough to be his daughter. They should have gone with a younger actor/character to make it more believable as a prequel. If that is what they're going for. Maybe they're aiming for an alternative universe/life for Bryan Mills.