After every Liberation Mission you get a prize depending on how many phases it took for you to complete the mission. This doesn't include Zenny prizes.

Prize	How to unlock
AntiNavi M	Beat Mission 4 in 9 - 10.
Anubis A	Beat Mission 9 in 14 or less.
BlakWing W	Beat Mission 7 in 10 or less.
BlizzardMan B	Beat Mission 1 in 6 - 7.
BlizzardManSP B	Beat Mission 1 in 5 or less.
CloudMan C	Beat Mission 3 in 8 - 9.
CloudMan DS C	Beat Mission 8 in 13 - 14.
CloudMan SP C	Beat Mission 3 in 7 or less.
CosmoMan C	Beat Mission 5 in 8 - 9.
CosmoMan DS C	Beat Mission 9 in 15 - 16.
CosmoMan SP C	Beat Mission 5 in 7 or less.
Fullcust *	Beat Mission 4 in 8 or less.
Muramasa M	Beat Mission 8 in 12 or less.
ProtoMan B/Colonel C	Beat Mission 6 in 9 - 10.
ShadeMan DS S	Beat Mission 7 in 11 - 12.
ShadeMan S	Beat Mission 2 in 8 - 9.
ShadeMan SP S	Beat Mission 2 in 7 or less.
Z Saber Z	Beat Mission 6 in 8 or less.