Starlight Glimmer's experimentation went farther than removing cutie marks.

Taken from his home and experimented with the DNA of another experiment, Spike is no longer just a dragon.

He is a new species altogether, and now has a partner-the former experiment.

Now, behold the Fierce King.....

Indominus Rex

(Totally inspired by Jurassic World, only dinosaurs appear so I don't think it warrants a "crossover" tag )