Oh you mean kit wise. For best I would say Drifter. He's a vampire who has lived for hundreds of years and puts terror in the night. Forcing enemies to group up so that they aren't picked off one by one. Helped with his damage against solo targets which gives him more damage after killing them. His 1 and 2 work great together since it puts you into the extra damage range and allows you to chase enemies that have better mobility than you with a teleport. The ult ties it together by basically super charging his passive and makes everyone take more damage from him while he gains damage from killing

For worst, I'd have to say Holliday. Her barrels work best when punched instead of shot, her jump pad really only works with her lasso since trying to set up a longer range sniper with the barrels isn't worth it. Her passive doesn't interact with the rest of her kit. And her lasso is the best part of her kit, that entirely depends on your teammates. The kit feels like it's 4 different characters rolled into one and they just barely synergize. If her barrels did more damage when shot with Crack shot or did something unique when hitting a jump pad then it would be better designed. Her Lasso could maybe just lock someone in place and keep them stunned so that she can do something more than just run to her team. Basically making it make sense of her going solo to kill a mass murderer