questionable

to a high degree; indicates doubt

to a great degree; a common and strong way to express doubt, often in formal contexts

to a very high degree; indicates strong doubt

doubtful from the perspective of ethical principles

doubtful from the perspective of moral principles about right and wrong behavior

to a moderate or reasonable degree; indicates some doubt but less strongly

used to state that something is doubtful or not certain to be good, true, or right

used to describe the process of something starting to be doubtful

used to state that something continues to be doubtful