Easiest- 4-F-4 because u bring Nasir, Ike, Micaiah, and Reyson.
turn one: Nasir uses a Laguz Gem (he has one). Reyson chants Nasir. Nasir Saviors Ike.
Since the spirits won't attack Micaiah or Reyson they'll all attack Nasir. Nasir gets no damage because of 1337 resistance, and even Sephiran won't do any damage (only like 6 with long range and 10 when Nasir's got maxed res for close range, where Micaiah can heal).
Anyway, Nasir gets no damage and is the only one attacked. PWNED. (btw to kill Sephiran I just cover the spots next to him with Micaiah, Reyson, and Nasir)
4-F-3 is also easy cuz u can just solo the map with Kurth and Ena (Ena attacks whites while Kurth attacks Blacks) And you bring Reyson and Micaiah for physicing when the AoE happens... maybe give Ena or Kurth Dragonfoe
4-F-2 is easy cuz u meteor/blizzard the boss with Soren and use Reyson to help if you need it. Then on the same turn you get everyone out of range (except for that one halberdier with a short speer in the middle) and wait with Ike (with Hammer). BK moves and attacks Ike, Ike does loads of damage (BK is off the 10 defence tile now) and then Ike finishes BK.
4-F-1 is easy cuz u bring shinnon and get the double bow and pwn everything
Hardest- 1-6-2 because i keep restarting whenever a green unit dies