The sentence "I haven’t saw him" has ungrammatical usage
Explanation:
Ungrammatical usage in a sentence refers to the incorrect use of ways of speaking where we can see different kinds of grammatical mistakes, a sentence with ungrammatical usage ins not coherent and doesn't make much sense, in this specific example it is incorrect to use the past form of the verb "see" with a perfect tense structure where we are supposed to use a past participle verb.