I feel Kwon Wang, should be your next victim, as he seems to only have spears and bow's as defence, not going for the heavy military units as Peter, DeGaul and Washington are.
As well, he has 4 Christian cities with Capital Seoul and Pyonang No's 1 and 2 being the only Islamic cities.
Peter, Has Moscow with his top 4 being his only Islamic cities, and considering his favourate civic is Beauracarcy, you'll need to convert Moscow to 2nd religion as well....
Personally I'd convert Thracian to Confussionism build a Monastry for conf, and spam Conf Missionaries out of there, to peters lands, gift them, send them do what you have to do...but spam them there.
Kwon Is set up for Christianity, but you have NO CHRISTIAN CITIES...so bad luck.
maybe bribe Peter or Degaul into war with Kwan won. Get him to use up those Hywa's...most of those horse archers, he's spammed.....then come inbehind once asked by civ you bribed..or just come in anyway after 5 turns.
Take out the 2 Islamic cities, being No's 1 and 2, he'll switch to Chirstianity, and be the next Pariah..Along with Washington, who only really has the "this war spoils our relationship -6" demerit.
Both DeGaul and Peter have a + 4/5 "we care for brothers of the faith"..DeGaul will be Neutral at best Peter being +1 AFTER peace is declared.
1) Convert Peter to Confussionism.
2) Bribe Peter to war with Korea
3) Enter into war after 5 turns or so..
Note, Korea, can be bribed into war with Peter, but for a high Price..Others will only make peace for Philosophy. Also, DeGaul has a SOD on the way to Washington, complete with Ele's/cat's