Omega: Initiating new test: subject Alpha group members to severe stress. Searching database for suitable event...
Omega: <bloop> Event found: the death of a comrade.

I bet the next 2 tiers will be of different worlds. The only FF games I know of where a comrade dies is...

FF7: Most likely, especially given that FF1-6 tropes have been done TO DEATH so far, and the Magitek Scorpion in the Ala Mhigo dungeon was the first major FF7 reference
FF4: Technically Tellah dies to Golbez and is your comrade. Yang, Cid all "die" temporarily as well. Fighting the Elemental Archfiends would be fun
FF5: Galuf dies, so if we retain the FF5 theme, we would fight more FF5 bosses, Azulmagia/Necrophobe/Nereid, etc
FF2: Josef dies, as does Ricard I believe. There's Astaroth, Beelzebub, Adamantoise and a few other notables.