This is only a few I can recall atm and some of the characters would definitely have to be ressurected John Snow style but:
Daenerys Targaryen (Emilia Clarke - Game Of Thrones) - IMO such an unjust ending to her character and tbf a rather anti climatic ending to probably one of the best tv shows I ever seen. Bring back Game Of Thrones Season 8 for a proper ending and make it 10 'bloody' episodes this time - I know, there's zilch chance of it happening and a guy can only dream of the possibilties of a re-run of the last season but this is one character I'd love to see make a comeback somehow.
Dexter Morgan (Michael C.Hall - Dexter) - A great TV Show that is based upon a a forensic analyst whose specialises in blood splatter pattern analysis and is also a serial killer. His victims are criminals that slip through the criminal justice system and on occasion other serial killers. Sometimes funny, sometimes dramatic and with a good solid cast alround, this is one character or tv show I'd like to see make a return.
Vic Mackey (Michael Chiklis - The Shield) - This is one of those under the radar cop shows that is brilliant but it's the character that Chiklis portrays that really steals the show in almost every scene he's in. Of course it was the whole Strike Team with Mackey at the helm that the series was about, in their almost vigilante style of blurring the lines between right and wrong. Gripping stuff and another great tv character that I'd like to see return to our screens.
Malcolm 'Mal' Reynolds (Nathan Fillion - Firefly) - One could argue that with this choice you'd have to include the whole cast, as good and as great as the tv show was and it still baffles me to this day why there weren't more seasons (not including Serenity) but the character of Mal Reynolds is excellent in this show, funny, witty, smart and it's one of those addictive shows that you can't stop watching imo
Vanessa Ives (Eva Green - Penny Dreadful) - An outstanding turn from Green in this show, by far the stand out performer imo and the last season didn't seem to do her character justice. She was excellent in every scene she was in and another character that would be great in a comback (tho she'd require the powers of Melisandre The Red Priestess to make any further outing) - a great show with a great cast but it's Eva Green's character that is the one to watch.