Nice selection on Dr. Sun...I really liked him in Tomb of Dracula, as well as his other appearances in Fan Four and Nova. First I saw him was Easter 1987 when I received the OHOTMU Vol. 2 Book of the Dead in my Easter Basket and I tracked him down because he was such a unique character.
Nefarius--Uh, not so much.
Thunderbolt--Yeah, not a bad character, but if I remember correctly he was an old guy with hypermetabolism. If you replace him with someone younger, now we are talking. I would actually team him up with Quicksilver in a maxi-series.
Others I would like to see revitalized or brought back from the dead:
Bragadoom--One of those obscure villains in Marvel Two-In-One, was a plant monster of some sort. Thought that he would make for a good monster villain for the Man-Thing.
Ulysses Bloodstone--One of those characters that had tons of potential but was killed off way too early. Yeah, Elsa Bloodstone is pretty solid and a hottie, but she has not been utilized well to this point. Bring back daddy dearest not as her mentor, but as her worst enemy and you have an excellent storyline.
Basilisk--The original Basil Elks. Appeared in Nova last year and really made me want another appearance.
Black Knight II--The Masters of Evil one that died early on.
Hammer & Anvil--Old Hulk villains, were cons that were bound together by a chain. Alien gave the chain and H&A powers because he thought it was their mating ritual (funny as heck). One was a white supremacist, the other a Black Panther. It seems like a Siamese twin in which one head can't stand the other (imagine Monty Python and the three-headed knight). Would be hilarious with Deadpool.
Actually Thunderbolt wasn't old. Chronologically, he was quite young. It was his hypermetabolism which aged him prematurely and he soon died of old age.