I think I watched Smallville before seeing Supernatural and The Vampire Diaries and even Leverage (lot of love for the actors!)
I'm currently doing a Marvel vs DC... well less of a versus and more of a merge of the Suicide Squad and the Squadron Supreme.
However I was just wondering if the Live-Action was it's own thing:
Smallville
Arrowverse
And the Animated Series:
Justice League/Justice League Unlimited
Young Justice
DC Superhero Girls
Harley Quinn TV Series
Etc,
Of course these fusions will have different names (both civilian and super), different backgrounds and origin stories, and even appearances.