frustrate

(verb) hinder or prevent (the efforts, plans, or desires) of. Synonyms: thwart, queer, spoil, scotch, foil, cross, baffle, bilk. Examples: "What ultimately frustrated every challenger was ruth's amazing september surge." "Foil your opponent."

(verb) treat cruelly. Synonyms: torment, rag, bedevil, crucify, dun. Examples: "The children tormented the stuttering teacher."