Wow, that is real brutal depthC

. I doubt that this has been caused my the other angel or blue ram...you would have seen them picking on him and I have never seen an angel with this bad of fin damage from other fish. His bottom fin is so far gone...I really hope he makes it.
I have to say it looks like someone is ripping him to shredds but because of the reasons above, I'm thinking its probably fin rot. Pay close attention to your other fish to see if this is happening to them. How long has it been since you bought them? I would deffinitly put in Melafix to help with this. Melafix has never failed me with fin rot or other fin damage.
Good luck, best wishes!