To get this trophy you need to learn all of Kimahri's "lancet" abilities or otherwise known as blue magic / enemy skills.
To learn a skill you need to bring Kimahri into the battle and use the move "lancet" on a fiend that has an ability you can learn.
None of these abilities are missable but nova would require you to fight Nemesis if you miss it from Omega and Nemesis is significantly more difficult.
After consulting the last person to unlock it Despairaporia, they claimed it popped a few seconds after learning the last ability.
Jump
Damage single enemy
Kimahri begins with this
Seed Cannon
Damage single enemy
Ragora - Kilika Forest
Sandragora - Sanubia Desert
Grat - Mt. Gagazet
Thrust Kick
Damage single enemy
YKT-63 - Bevelle Highbridge
YKT-11 - Yevon Dome
Aqua Breath
Water damage to all the enemies
Chimera - Macalania Forest, Al Bhed Home
Chimera Brain - Calm Lands
White Wind
Recovers half of the HP of all the allies
Dark Flan - Mt. Gagazet
Spirit - Omega Ruins
Mighty Guard
Cast Barrier and shield to all allies
Behemoth - Mt Gagazet, Zanarkand Ruins
King Behemoth - Inside Sin
Fire Breath
Damage by Fire to all the enemies
Dual Horn - Mi'hen Highroad, Mushroom Rock Road, Al Bhed Home
Grendel - Mt. Gagazet, Zanarkand Ruins
Valaha - Sunken Cave
Self Destruct
Sacrifice yourself to damage one enemy
Bomb - Mi'hen Highroad, Mushroom Rock Road, Al Bhed Home
Grenade - Mt. Gagazet
Puroboros - Omega Ruins
Stone Breath
Petrified state to all enemies
Basilisk - Djose Highroad
Anacondaur - Calm Lands
Doom
The enemies die in a number of turns
Ghost - Sunken Cave
Wraith - Inside Sin, Omega Ruins
Bad Breath
Causes several altered states to all enemies
Malboro - Calm Lands, Sunken Cave
Great Malboro - Inside Sin, Omega Ruins
Nova
Damage to all the enemies
Omega - Omega Ruins
Nemesis - Monster Arena
Also, you should be able to learn from the Ronsos at the Mt. Gagazet.
Just use Lancet if they start using the skill.
- Yenke Ronso: Fire Breath, Aqua Breath, Stone Breath, White Wind
- Biran Ronso: Thrust Kick, Doom, Self-Destruct, Mighty Guard