Space Marines: Bikes with those stupid square section wheels!
Space Wolves: Ragnar Black Mane ever ones favourite space wolf hammered flat.
Blood Angels: Mephiston for the same reason as Black Mane... looks like he has been squashed with a size 15 boot.
Dark Angels: OK so this one would fit in any Marine section but Captain in Terminator armour. He is tiny compared to normal terminators and looks stupid leading The Death Wing to war.
Grey Knights: All the assassins. There either flat, static or in stupid poses. In some cases all three!
Chaos Marines: Kharn is static when he should be charging.
Chaos Daemons: Blood Thirster because he looks so badly dated with those great big hands and huge blunt teeth.
Tyranids: Genestealer there so iconic thanks to space hulk I feel they need a better model... and stronger rules on side note.
Necrons: C'tan shard of the Deceiver really stands out to me as a totally pump model.
Eldar: All the Phoenix Lords. They should be the amazing but like Ragnar and Mephiston old moulding techniques make them look flat and boring.
Dark Eldar: Drazhar... Master of blades... does not seem to be holding swords!
Orks: Er none... I like them all!
Imperial Guard: Leman Russ X 10. The tank is tiny and the turret is too small!
Tau: Vespids... Oh what a nice model I've designed... there is just a little something missing... Brian pass me that hammer whack whack whack. That’s better nice and flat.
Adepta Sororita: Uriah Jacobus whack flat!

There are of course lots that need a re-work but these seem some of the worst to me!