He has been suppressing an awful lot. Boku!Suzaku may be forgiving and unwilling to cause any unnecessary damage, but this is the same boy who stabbed his father in the stomach seven years back. He's more than capable of violence, especially when he's this bitter and enraged. Also, he's not holding back at all on a man who he feels embodies everything he hates—"an existence that's a mistake." Specifically, Suzaku's mistake for not preventing him from pursuing patricide all those years back.
(no subject)