I would be very interested in reading about any established Protestant Church burning any Catholic at the stake. Can you point me to any such history?
You could start by reading up on the career of John Calvin. Then proceed to Henry VIII. Then find out what happened to the last Catholic priest in Iceland. That's just for starters.
If that isn't enough, you can pick up a book on the Thirty Year's War.
The Anglicans tortured and killed many Catholics, in addition to seizing their property, forbidding Catholic worship, and destroying Catholic liturgical items and art. Other Protestant denominations killed mainly other Protestants. Calvin was particularly bloody. But then it turned around and the whole reason the Puritans (Calvinists) fled England was because of their persecution by the established Protestant church there.
In short, you can find this anywhere.
The dispute between the Armenian and the Greek Orthodox has nothing to do with doctrine, but is probably more ethnic in origin than anything else. I’ve never been sure how the Armenians ended up being one of the groups in charge there, but historically these groups have never gotten along with each other.
The Franciscans represent the Latin Rite churches there, and quite often there have been conflicts between them and the Orthodox churches, too. But again, it’s more ethnic or cultural than anything else.