In the update of the MSD v1.22.1, there are 5 more special missions added: 96th to 100th
This post, however, is about the special mission 100th.
In fact, at first sight, the 100th mission is indeed a challenging one. The developer purposely adds a number of troops in the deck (including the Donald Morden and the Sol Dae Rokker). However, they are playing no roles in this mission!
Indeed, this 100th mission is a one man show. Our main character - ALLEN O'NEIL!
Correct, just summon Allen O'Neil as many as you can, and as fast as you can. The enemy boss could be defeated easily.
Perhaps this is the mission that the developers would like to convey a message that, Allen O'Neil is something not to be belittled. He has quite a sustainable Hit Points. During the battle, his special skill 'grenade throwing' causes a significant damage to the boss. That explains why he stands out in this mission.