Collocations for suicidal - adj.

be, feel, look, seem, sound
become, get
He became very depressed and even got suicidal at one point.

almost, nearly (esp. AmE), potentially

be, prove
seem

financially, politically
a move which would be politically suicidal

potentially, seemingly
a seemingly suicidal plan

downright
ultimately

for
These policies would prove suicidal for our economy.

Suicidal is used with these nouns:
behaviour, impulse, maniac, tendency, thought