The Dr. Fate-Ality Achievement/Trophy is very simple to get and can be done in both "
Versus" or "
Single-Fight" depending on if you have a spare controller handy.
Choose your mode and characters then select the level "
Gotham City" Empire Theatre". Once you load into the level use either RB (XB1) or R1 (PS4) to kick the enemy into the Theatre 3 times and the this will unlock.
Here is a simple video guide if this helps you better then a written guide.