For high damage combos I used S'asshole's juggles and for most juggles I used p-bot.
Even without Rage powerup, S'asshole can rack up good combo damage, jsut may be a bit diffacult to juggle because you have to move and aim him. I like to wait will my opponant picks up the weight and becomes bigger
I've been playing DTD before I found this site, so the challenges both came easy ^^, but this is a seriously addicting game, and was designed greatly, think this is fun... do the "THE 100" in challenges >:)