The Terrible Trio is a name used by more than one supervillain group in the Marvel universe.
The earliest was a group of criminals given enhanced abilities in order to take on the Fantastic Four. They prove to be surprisingly challenging for a band of thugs but are repeatedly foiled throughout the 1960s.
The second Terrible Trio was an unrelated group of villains who banded together to harass the hero Nova in the 70s.
References: [wikipedia.org: Diamondhead (comics) ]
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Metahuman Database 