Trixinite

A Trixinite form is a triple-evolved form of an alien.

How to do so
To turn into Trixinite form, you must turn the omnitrix 90 degrees clockwise, and then turn it 180 degrees counter clockwise, and then press down. The omnitrix will turn blue before you press down to let you know that you are going into Trixinite form.

Trixinite Forms
The known Trixinite forms so far are...

Xlr8

Ghostfreak

Heatblast

Snare-oh

Big Chill

Swampfire

There will be more, but for now these are the only ones.