absolutely , apparently , assuredly , clearly , easily , for sure
probably, presumably, most likely
Doubtless means likely, probably, almost certainly. "My name is Bond. James Bond. Doubtless you have heard of me."
It was doubtless that they intended to proceed with their mission.
"It was doubtless they would have to attend the class."
By itself, 'proclaim' is neither. It is simply a verb. A synonym is a word with a similar meaning. To state, declare, say etc are synonyms of 'proclaim'. But to give examples of antonyms (opposites) of proclaim is a little trickier. Not all words have antonyms. But doubtless someone will suggest a few....
Doubtless there is a firm called Gerber somewhere.
They are synonyms.
Synonyms
Doubtless many questions appear 'dumb' when you know the answer. Doubtless many 'dumb' children ask unnecessary questions. The reasons they do so are as varied as those that ask them.
Relative and kin are synonyms.
Doubtless he was. As have we all at one time or another.
Yes, doubtless many jazz musicians are atheists.
They are synonyms.