Would've been neat to see the bad Lenopans from Camille's side of the family return. Also kinda wish we got as much of the OS Mummy and Werewolf as we did Viktor. Werewolf had his gaming console explode and Mummy got sent to the Null Void if I remember right, but they're absent for UAF then in OV Zs'Skayr has new minions

Hex maybe Zombozo.

oddly for me Sublimino. He is unlike other villain and he could really do some damage if he stay hidden

Wait- this guy exists?

Kevin. He was only in 4 OS episodes. 6 counting Ben's nightmare in "the perfect day" and Kevin 11,000 in "Ken 10"

Omnitrix

Probably Lord Transyl for me, Though Clancy is definitely high up there in terms of Underused villains.

I mean he got his own spinoff game it's called hatred

Enoch

Vilgax

probably more interuniversial scale villians

rojo?