[SymbioticFunction]

It actually doesn't bother me that Last Jedi shows that Luke momentarily heavily considered killing Kylo Ren.

Whilst it's obviously the old 'if you could go back in time, would you kill Adolf Hitler before he could rise to power' conundrum, we also saw Luke seriously attempting to kill his father in Return of the Jedi.

In ROTJ, it's only when he sees the similarity of Vader's missing hand and hears the Emperor's approving voice that he decides not to follow through. So Luke considering killing a relative who is affiliated with the force's dark side is really nothing new for the franchise.

Also worth noting that in Revenge of the Sith, jedi master Mace Windu wanted to summarily execute an unarmed Palpatine because he thought it was too dangerous to let him live. So prior Lucas lore also lends credence to the flashback events in Last Jedi.