AAAAALRIGHTY let’s just go ahead and nip this one in the bud right now okay
the “Tadashi will come back as the villain” “rumours” were started by this article from a while back that didn’t really pick up traction until this whole “Stan Lee confirms Big Hero 6 sequel” thing
if you actually read the full thing rather than just the clickbait headline you’ll see that the entire argument being presented is literally 100% speculation and theories by someone with absolutely zero affiliation with either Marvel or Disney that managed to somehow get interpreted as official “rumours” because of how badly the headline was written
he also seems certain that Tadashi will come back as Sunfire, despite Marvel not owning the rights to Sunfire because he’s a part of the the X-Men, which is owned by 20th Century Fox
this exact same thing happened around this time last year with all those initial Frozen 2 “rumours” about Elsa getting a boyfriend and look how that turned out
can we all just take the time to actually read shit instead of spreading around misinformation
TL;DR: NONE OF THIS IS EVEN REMOTELY OFFICIAL, IT’S ALL BASICALLY FANFICTION WRITTEN BY A FAN THAT HAS BEEN MISINTERPRETED AS FACT BECAUSE OF THE POORLY WORDED CLICKBAIT HEADLINE