Collocations for harmless - adj.

appear, be, look, seem, sound
make sth, render sth
chemical wastes which have to be rendered harmless

consider sth

absolutely, completely, perfectly, quite, totally
almost, virtually
enough
He looks harmless enough.

comparatively, fairly, mostly, pretty, reasonably, relatively
apparently, seemingly
a small and seemingly harmless creature

environmentally

to
The substance is harmless to people.

Harmless is used with these nouns:
fun, substance