He wanted to threaten Loki, but Loki interupted him by sneering and saying, "Or you will what? What else can you do? Will you overload the reactor in the suit and commit suicide in hopes of taking me down with you? Trust me, I can take it."
His words choked Greg up. When he could speak again, he said, "Fuck you!"
The truth was that he contemplated committing suicide and had tried to use the possibility to threaten Loki. But now that Loki had guessed his last card and had assured him that he could handle the explosion of the reactor, Greg felt that he couldn't use this threat anymore.
The problem was that he didn't have anything else to use. Without the threat of suicide, there was nothing else that he could use to threaten Loki and make Loki stop trying to kill him.
So after racking his brain and failing to come up with something to do, he said to Loki, "Fine. Fine, you win."
Then he turned around to escape.
