Synonyms for Weaken (same or very similar meaning)
WordNet sense 1 (destroy property or hinder normal operations):
counteract, sabotage, subvert, undermine, countermine
WordNet sense 2 (lessen in force or effect):
break, damp, dampen, soften
WordNet sense 3 (reduce the level or intensity or size or scope of):
de-escalate, step down
From the ODE community, based on WordNet
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