If "It's" is compressed form of "it is", then it is incorrect to say "It's biggest competitor would be..." rather, it should be this way, "Its biggest competitor would be..."
When do we use "it's" in a sentence anyway? Or is "its" grammatically incorrect?
It`s is the contracted form of "it is"
e.g. It is not known who did it.= It`s not known....
"Who`s this pen"? "It is [It`s ] mine".
Its is a possessive adjective or pronoun depending on the context you use it.
Its tail [ the cat`s tail]is long. -possessive adjective
It is its[ it is hers -of the cat] -possessive pronoun