I read this as an ebook, probably a Kindle book, in the last five years or so (so read within 2015, although I think the book was older). The protagonist is a teenage male who does something involving saving a girl (I think associated with a prominent politician?) of about the same age in a situation involving alien invaders. He wakes up to find out he's been convicted of a heinous crime with his punishment being put into a suit that gives him powers to fight aliens who are trying to invade Earth. I vaguely remember that the powers are semi-random, but generally involve a combination of increased toughness and the ability to spout various energy beams. I think there is an established hero team who usually takes credit for the victories. The expectation is that most such convicts will die in battle (and many do), but he actually survives, through a combination of luck and exploiting the system. I think the girl he saved becomes aware of him, and starts an effort to bring him back to a normal status.
I remember there were multiple books in the series, and I think I actually bought the second one in the series, although I think I balked at buying later entries, although I don't recall why.