Fulsome is often used to mean “offensively flattering or insincere.” But people also use the word, particularly in the expression fulsome praise, to mean simply “abundant,” without any implication of excess or insincerity. This usage is all right, but it may invite misunderstandings in contexts in which someone could infer a deprecatory interpretation.

You may unintentionally offend someone by saying I offer you my most fulsome apologies, where the use of an adjective like full or abundant would leave no doubt about the sincerity of your intentions