Redeemer and Minnie vs Mimi is a battle that takes place in Heaven. The battle was not shown in the comic so not much information is known about the battle.
Redeemer took Minimandy´s spirit along with him to Heaven after she got ripped apeart by the Pumpkinator and gave her powers to Grim Jr.. When Redeemer and Minnie arrived at the gate of Heaven, Mimi appeared to battle them in order to take Minnie with her.
The battle wasn't seen but all that is known is that Mimi cut off the hand of Redeemer and somehow got Minnie unconscious and took Minnie with her.