Correct spelling, explanation: competitive is an adjective from the noun competition. This word comes from the French compéter (meaning be in rivalry with) or directly from Late Latin competere (meaning strive in common, strive after something in company with or together). In this case, -e changes to -i, not to -a, therefore the form competative is incorrect.

Definition of competitive:
adjective, someone who likes to rival others
I don’t want to play soccer with him, he’s too competitive.
She’s very competitive, that’s the reason she got into university.

Incorrect spelling, explanation: words ending with -ive are adjectives, which means there are derivatives of nouns or verbs. The basic word is the noun competition, not competation, and the adjective must coincide with its root. This is why the right form is competitive, not competative.

Incorrect spelling

Incorrect spelling