The Most Powerful Villain Army in Comics/movies/books

Darkseid's Parademon after capturing Superman and taking his DNA and giving to the Parademons. This made the parademons almost make like Superman.

Also wanna throw out the D.R.A.G.M.A. from Godzilla: The Series (because I've been binging it). They reduced the US population to a few thousand and killed all other Kaiju on the planet. They also adapt to whatever they're attacked with, so think of them as an army of flying Triceratopsian Doomsdays.

The Beyonders murdered the Marvel multiverse, including the Living Tribunal

The Annihilation Wave

Paradooms from justice league dark: apokolips , genetic hybrids of Parademons and Doomsday makes them very powerful.

Eternal Empire from Star Wars Legends (The Old Republic)

The Minndless ones from the dark dimension.
The Builders from marvel

The witches from Shrek 3 were pretty OP

The Galactic Empire was pretty solid. They conquered and maintained control over the galaxy for decades

The Borg is pretty powerful.