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.