Storytellers love to stress that any evil being who threatens the heroes must be eliminated for the good of us all, but since the stories end with goodness prevailing we never get to see what life under an evil thumb would look like.
It's said to be horrible, with lots of enslavement, torture and skin flaying, but the baddies who simply work you to death don't really seem so bad after all, since it's easy to both skip out on work and fake your own death.
Bowser can't even keep track of the stuff that goes on in his own castle so life under his rule would be pretty much the same, only with more turtles and spikes.
And, as this JHALL comic shows, Loki would realize he made a horrible mistake ten minutes after he subjugated humanity- because humans are awful!
See What Would Happen If Fictional Villains Actually Won here