In legal|lang=en terms the difference between intentional and proposal

is that intentional is (legal) done with intent while proposal is (legal) the offer by a party of what he has in view as to an intended business transaction, which, with acceptance, constitutes a contract.

As an adjective intentional

is intended or planned; done deliberately or voluntarily.

As a noun proposal is

that which is proposed, or propounded for consideration or acceptance; a scheme or design; terms or conditions proposed; offer; as, to make proposals for a treaty of peace; to offer proposals for erecting a building; to make proposals of marriage.