I'm looking for a word that is roughly the opposite of "intimidating", but with negative connotations. I'm not looking for something like "reassuring," more like "wimpy" or "beneath notice" or "unimportant," perhaps even "tempting others to attempt intimidation," but nothing I've found quite fits the bill.
I'm wanting to say something like, "He was a nice enough guy, she thought, but it was an effort just to take notice of him. He was ???"