I would say that, as a "twisted" person himself, his view of the world is that anything that harms, but does not kill, warps and corrupts your mind or body until you might as well be dead.
The original phrase ("...makes you stronger.") implies that people get better from being injured. This means the opposite, people change for the worse from injury. They don't die outright, but suffer a kind of "death from a thousand cuts": each suffering moves them slightly from their original self (possibly going back to what they were at birth, the "tabula rasa") until they are effectively dead compared to their original self. Maybe lacking any compassion because they have been victimized too many times, or trust because they have been cheated on and defrauded when trying to love and help. Eventually the original self would, if still alive, be so alienated from what it became it would disown itself as being "dead to me".
Did this answer your question, or did I just ramble nonsense? Let me know and I will revise it.