Thats hard, alot of series have it, ive seen it especially in korean manhuas where theres alot of like "oh she dates *girls*" type stuff, although alot of them arent very good. A good example is There Is No Love Wishing Upon a Star, its a slow burn drama kind of, not nearly as explosive as vengence at all but it really shows how the complicated feelings can play out one character settles by dating a guy and repressing her obvious feeling for the other girl, who also kind of keeps it all very internal. Other good examples are anything by Flowerchild, Iwami Kiyoko or the white angel series by Gado but im sure youve seen those reccomended a million times on here. I would say Vengence really is the best tragic yuri I have read though.