Collocations for legitimate - adj.

be, seem
consider sth, deem sth, regard sth as, see sth as
make sth

completely (esp. AmE), entirely, perfectly, quite, totally (esp. AmE), very (esp. AmE)

Legitimate is used with these nouns:
aim, argument, authority, business, chance, claim, complaint, concern, contender, criticism, daughter, demand, disagreement, dissent, excuse, exercise, expectation, expense, fear, grievance, ground, heir, interest, means, purpose, reason, request, ruler, self-defence, son, tactic, target, trade, use