I certainly agree that even the most heinous of criminals should be forgiven, but that that doesn't necessarily free them from the consequences of their actions. Does loving our enemies mean that we should not execute them either, even if it is in retribution for murder? The Bible does say that vengeance belongs to God...
I am opposed to executions by the state, in part because I oppose the State's existence, but I haven't ruled out justice being administered by private means in a voluntarist society (perhaps my views are still too primitive to rule out any death penalty 😄).