Stultify

1. verb

   prove to be of unsound mind or demonstrate someone's incompetence

   “nobody is legally allowed to stultify himself”

2. verb

   deprive of strength or efficiency; make useless or worthless

   “This measure crippled our efforts”

   Similar: cripple

3. verb

   cause to appear foolish

   “He stultified himself by contradicting himself and being inconsistent”