Since the only way "Dark Necrofear" could be part of the "Last Turn" battle is if she is already on the side of the field of the player activating "Last Turn". So let's use this as an example:
Player A activates "Last Turn" during Player B's turn and selects "Dark Necrofear". (We'll assume that "Last Turn" is activated AFTER Player B's normal Battle Phase. I'll explain why later).
Player B special summons "Invader of Darkness" from his deck.
"Invader of Darkness" attacks and destroys "Dark Necrofear", sending her to the graveyard.
Now, during the end phase, Player A has 2 effects that need to be resolved, "Dark Necrofear" and "Last Turn". Since Player A wants to win, he resolves "Dark Necrofear" first, returning her to the field as an Equip card and takes control of "Invader of Darkness". Then Player A resolves "Last Turn" and claims victory since he has a monster on his side of the field and Player B doesn't.
Now to explain why if this was activated before Player B's Battle Phase, Player A would lose.
Same example as above with "Invader of Darkness" destroying "Dark Necrofear". Now when Player B has his Normal Battle Phase, he can attack with "Invader of Darkness" and reduce Player A's Life Points to 0 and win the duel before even reaching the end phase.
So remember, timing is everything.
- A