I like Larloch… because he is crazy and lawful evil. He is obsessed with learning more about magic and being left alone to do it. So any pact can be good or evil as long as its supports one or both of those goals. If its weird and only half makes since, its even better because is detachment from normal sanity means what makes since to him might not even seem believable to normal people.
I made a warlock of the undying who has Larloch as a patron because the warlock thought he was going to die and made statement in self defeat discarding all hope... "go a head and kill me?!?! Why not you have taken everything else from me!?! If your just going to steel ever thing and leave me with nothing your just a thief!" … Larloch wasn't paying attention to this ant but herd the last part and made him warlock in trade for the corpses of the mans family he just turned to zombies to resupply his staff. It is kind of what the guy said, but he never expected an actual trade. Larloch is lawful evil and the proposal made curtain since, and he was full up now no zombie servants... Now this warlock hates his patron with a burning passion while at the same time being utterly terrified of him. So the warlock is building his power for eventual revenge in the Warlocks Tomb but is too scared to not comply to "requests for information" that the patron might send. A good guy in a pact with an evil patron, doing his bidding on a rare occasion, while wanting nothing more than the destruction of this evil.