Damien Darhk - DC's Legends of Tomorrow
The best villain on TV lives! At least for a short time. He was killed by Oliver Queen on Arrow in retaliation for Laurel's death but returned in some timeline escapade on Legends of Tomorrow. He finally died for good when he sacrificed himself for his daughter, Nora. Even villains can have heart.
Dan Conner - The Conners/Roseanne
Um, okay. So Dan died of an apparent heart attack in the final season of Roseanne which was an entire work of fiction written by Roseann herself to help her deal with Dan's death. Then in The Conners "revival", everything else was fiction, too. Well, at least we think it was because there was never a true explanation of how Dan came back to life.
Jessica Logan - Timeless
Time travel is a nifty thing until it messes with your current life. Wyatt might have thought his wife was dead, but she wasn't (of course) and returned just in time to add a bit of drama into his relationship with Lucy.
John Winchester - Supernatural
Make a wish with a Chinese genie box and hope it comes true. Although John's spirit had once returned to save Sam and Dean from the heathens of hell, he returned again in Season 14. It was a beautiful moment seeing John reunite with Mary and his kids, but it didn't last as John had to return to the timeline from which he came.
Elizabeth Keen - The Blacklist
Liz wanted to get out from under the thumb of Red so she worked with Mr. Kapland and Tom to stage an elaborate death. The team was devastated they had lost a colleague and Red's grief was beyond words. When everyone found out she faked her death and was alive, there was a lot of well-deserved resentment, anger, and hurt.
Jimmy Lishman - Shameless
What happened to Jimmy Lishman? Who knows, but he was dead and returned on Shameless Season 4 with a new name and a new life.