Underworld vs True Blood
OK, let's get into it....
Team 1: Every Vampire/Lycan/Hybrid/Whatever from the Underworld movies. Selene and all of them, all banded together.
versus
Team 2: Every Vampire/Shifter/Wolf/Witch/Whatever from True Blood.
Each team has all their resources/gear/weapons/spells/powers/feats. Anything goes. Bloodlust is on, no morals.
Who wins?
Well the Lycans are definitely more powerful than the useless werewolves of True Blood, but the older vampires of True Blood are just too strong and too fast. They can freakin fly. Then there's the witches as well who are quite strong in their own right.
True blood wins this. The only hope of the Underworld universe are their hybrids, but the hybrids are just plain outnumbered by the older vampires of True Blood.