>>39061657He's a petty crook and an outlaw, but not a murderer or a slave trader. Wes was cool with Snagem's outfit until he got wind of their bigger operation; he just wanted to make a living on his side of the law and when he found out that Snagem was really the supply side for a big conspiracy, decided it was too big to let go.
He doesn't give a shit about the kind of crime that normally goes on in Pyrite, but draws the line at kidnapping, trafficking, and building personal armies out of brainwashed Pokémon. So Wes figures he'll blow up Snagem's base and use the Snag Machine to take what he wants for himself; then he stumbles onto Rui and gets a chance at blowing up the other half of the operation too. Dude loves his fireworks.
I figure by the end of the game he'd fallen so hard into the hero gig it'd be too much trouble to walk out on it, so he decided to give up stealing Pokémon and went off on a journey to return all of the ex-Shadow Pokémon to their rightful owners.