-some the suffix, means characterized by. We see it in awesome, gleesome, tiresome, winsome, et al. Whether one of these words is considered to be negative or positive is dependent on the nature of that characterized.

The earliest definitions of fulsome seem to include both the copious and the cloying connotations. This should be a little disconcerting to the careful user of the language. Perhaps a less equivocal word could be chosen.