frustrate implies making vain or ineffectual all efforts however vigorous or persistent.
frustrated attempts at government reform
thwart suggests frustration or checking by crossing or opposing.
the army thwarted his attempt at a coup
foil implies checking or defeating so as to discourage further effort.
foiled by her parents, he stopped trying to see her
baffle implies frustration by confusing or puzzling.
baffled by the maze of rules and regulations
balk suggests the interposing of obstacles or hindrances.
officials felt that legal restrictions had balked their efforts to control crime
Middle English foilen "to trample, tread upon, mortify (the flesh), oppress," alteration of fullen "to full (cloth), trample down, oppress," perhaps by analogy with loanwords from French with palatal l that result in variants with -oi- and -u-, as coilen, cullen "to select for quality, pick out, cull entry 1" — more at full entry 5
Middle English, leaf, from Anglo-French fuille, foille (from Latin folia, plural of folium) & fuil, from Latin folium — more at blade