I noticed that both Coliseum of Strife and a lot of purple cards synergized quite well with making cards fragile. Blast effects, the Parsa Divinity Cannon you get from Jaza'eri Arquebus, Racer in Shadow, and even Knives in the Dark love facing off against Fragile minions. The best synergy of all is probably the Born in Cruelty card generated by Merciless Koxinga. Shadhavar Beast, Wry Trickster, and Misfortune all help make the enemy minions Fragile. I think Shadhavar Beast is particularly underrated currently as an enabler of Coliseum of Strife, as it also lowers the enemy minions' attack to help you survive trades.

Video

https://youtu.be/ZGaQSzqVlUo