Sinless, a.
Free from sin. Piers Plowman. -- Sin"less*ly, adv. -- Sin"less*ness, n.
Shades of meaning
Fernald has no entry of its own for sinless; he lists it under innocent, perfect.
Where he writes about it:
Immaculate, pure, and sinless may be used either of one who has never known the possibility of evil or of one who has perfectly and triumphantly resisted it. — from innocent