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[Mighty Midget]

It doesn't matter if the square removed is just next to Angel or lightyears away. The main point is that from Angel's point of view, that removed square puts a limit in only one of 8 directions, at the most. With only one square removed, a maximum of one direction is closed, leaving Angel to choose from any of the other 7. If we ignore any diagonals and just look at the horizontal/vertical movements, that still leaves three movements.
All Angel has to do to make sure Devil never traps him/her/it, is to always move in one of two directions say, down and left, and never up and right. That will always give Angel an escape route.