This scenario is a bit off for a 'boss fight', but oh well. :) I imagine your character killing an ex lover or such.
More of a tragic setting, but I see it started with polishing the dagger used for the killing.
Then, you would relive the act of betrayal in your mind before traveling the dimly lit hallways of the estate.
You would confront them and they would vehemently deny the allegations.
Still, the facts remain unchanged and it becomes depressingly clear they never loved you.
The anger builds once more as an argument ensues.
You scream back and forth at each other and they reach out to strike you.
As you recoil from their attack and feel the heat on your face from their hand.
You reach under your skirt and pull out the dagger, clinching it tightly in your palm.
You lunge and send the blade deep into their chest, slowing the beating of their lying heart.
As they reach out to you from the pool of blood around them, you only look at them with disdain.
While the light fades from their eyes, you swear to never again fall victim to the perils of love.
Anddddd that opened a new chapter of 'dark and slightly crazy' in my writing.
That was kind of fun. ^-^
Sorry for deviating a bit from the thread topic!