The Kevlar vest would indeed be a good option - especially as when Loki thrusts, he aims for the meaty part of the right shoulder. It's a clean jab and, hardly fatal and not all the way through, but more than enough to keep Steve in place while they have their chat.

"Ah, ah, ah... Now was that polite? I asked you a question, captain." He crouches, cloak pooling around him as his knee jabs in between Steve's shoulder blades. "And it's the sort of question that demands an answer." Since Steve can't see, his smirk warps into something feral; but his voice remains civil and commiserating. "What if I were to tell you that with a word I could wind back the clock for you? That I could return you to the world as it was, with all the familiar faces I'm sure you find yourself searching for in the crowd. Hm? Thoughts?"

He jars the point of the spear, using the pain to emphasize the other point he hopes to impress upon the spangled one. "I'm really quite magnanimous when you get to know me."