abnegator

from The Century Dictionary.

• noun One who abnegates, denies, renounces, or opposes.

from the GNU version of the Collaborative International Dictionary of English.

• noun rare One who abnegates, denies, or rejects anything.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun one who gives up or relinquishes or renounces something