have you ever heard the phrase, kill them with kindness?
also another great one, keep your friends close but your enemies closer?
so what you should do is be really nice to bardock, befriend him, maybe somewhere along the way he thinks oh yeah time immemorial we've had some disagreements but now i trust you and he invites you to dinner, just like he does with all those migrants he lets have their way with his gf..
THEN..thats when you strike! poison him or smack him or whatever you wanna do