Destroy every capital city from the inside with a cult(following the ideals that humanity will be remade upon its destruction) who've grown up the political(or whatever their power system is). Causing mass riots and civil wars decimating any worthwhile resistance. Upon completion of this I'll simultaneously burn any resources and assassinate anyone left who would pose a threat(shows extreme leadership skills, etc). While the resources burn the water supplies of every major country will be poisoned resulting in more chaos and destruction.
After this I'll pull my cultists back too our base of operations while we will wait out the inevitable destruction. After the population has culled i will send my cultist to begin curing the water supplies and scavenging parts to slowly rebuild society.
You said end the world, it's ending it in a way...
Oh and if any of my cultists have a "change of heart" mid-way they will be made an example of in front of many. Not killed but tortured to the point of it.
I'm not evil
i just have alot of free time to think about how i would end it...