>>42752216
Well I'm sure there must of been martyrs, especially during the three tribes period. But as for super famous martyrs in Equestrian history, I would say it would probably be Star Swirl the bearded or Princess Celestia, but I don't think they fit personally.
Star Swirl isn't exactly well known except for Luna, Celestia, Twilight, and probably some other intellectuals. Celestia sacrifices, yes, but she herself wasn't killed, but is still admired in everyday life for her sacrifice.
On top of that, both weren't killed, so martyr isn't the right word to use for them.
Due to the peaceful nature of Equestria, no one killed, or at least killed in a fashion that would put them in the same class of influence as JC while also being considered a martyr. Still, Celestia is pretty close I think since she has great influence, powers, and inspires people to act more like her, along with her disciples, the elements of harmony, who are against the devil, Nightmare Moon.
That's the best answer I can come up with. I hope you're alright with it Anon.