"Your enemies are still your neighbors" is entirely consistent with those statements and in fact was how it was understood by the consensus mainstream of christianity until very recently, and is still how it is understood in most variants other than american protestantism.

> Yes however in Christian theology it's both forgiveness _and_ repentance (which requires a penance), thus it doesn't mean you are free of consequences just because you have been forgiven.

Indeed, but for this you need to let the person in question time to realise their errors and repent, which is impossible if you kill them.

> Additionally, loving your neighbour means calling on God's mercy which is willing the Good of the other (the definition of "what is good?" is answered differently in Christianity).

Calling on God’s mercy does not imply playing god ourselves and disposing of the lives of others.

> Finally, not everyone is your neighbour (Jesus also acknowledged his enemies in Luke 19:27).

It is not really relevant in this case, though. Murderers can be Christian as well and accept his “reign”. But yeah I take your point: the bible has a lot of inconsistencies.