He shows up to the house and has a gun, he doesn't kill Clementine.
(Hypothetical) We don't know who killed the Walkers that got Pete and put him down but it could very well be Carver's group who was doing him a mercy.
He shows up and kills all the Walkers that are overwhelming the group and only begins to strike Carlos after Carlos spits on him, using his pain in an attempt to bring out Rebecca. He threatens to kill people if Rebecca doesn't show up but he never does, he's only threatening to do so.
He only kills Walter after Kenny's shot one of his men as a one-for-one trade and uses human shields to get Kenny to come out. He spares Alvin if you get Kenny to stop shooting.
I don't think Carver is the nicest person around but I don't think he's as evil as the group paints him to be, he has an entire community under his thumb and he appears level-headed and making decisions based on circumstances rather than going for the immediate "kill everyone because lol".
I don't trust Carver but he's as trust worthy as Luke and his group, the only people that I can trust being Kenny.