Highlander had an arc about how since immortals absorb each other's Quickening, ones who spend their lives killing evil immortals risk being overwhelmed by them.
And the Sith willingness to taunt people into killing them less Pyrrhic. It's a legitimate victory.
Love and connection and a refutation of some Jedi tradtions seems almost like a prerequisite for becoming one with the Force in the way that Obi-Wan did.