I could probably list like 20 champions, but that'd just be a waste.
Karma - from what I've seen and played, she has a decent early laning phase, being able to clear out any wave with a q + e (with r) combo, but her lack of an ultimate really does hurt her. Give her 3 mantra stacks or remake it imo.
Sejuani - just doesn't feel strong enough. Her ult is powerful enough to be her q, w, or e, but really doesn't deserve it's place at r.
Volibear - Suffers from the same thing Garen had. Good early game that could be easily countered leading into a "meh" at best lategame.
Those are three that personally I think need some good tlc.