Missing certain skills is not the only concern when it comes to mastering all Enemy Skill Materias in “Final Fantasy VII”. Some skills must be learned by other means, such as White Wind. This skill is used to heal, and since monsters generally wish to defeat the party as opposed to heal them, the ones with this skill will never cast it on an enemy.
So, in order to learn this skill, other Materia must be used. The player has to either confuse an enemy with the White Wind skill and hope that the AI decides to cast it on the player, or use the Command Materia Manipulate, which allows the player to take control of an enemy and decide it's actions for a set time. This is the better option, as the player can simply select White Wind from the enemy's command prompt and have it cast the spell on the party.
One other interesting type of Enemy Skill that can easily be missed is Pandora's Box. This is learned extremely close to the end of the game, in the North Crater on disk 3. Pandora's Box is the most powerful Enemy Skill in the game, dealing physical damage to all enemies in battle, but for a hefty cost of 110 MP.
It can only be learned by a Dragon Zombie, and the part that makes it so easy to miss is the fact that it is used as a death cry, which in any other case would make it extremely easy to get. However, the Dragon Zombie uses the skill only once per save file. This means that if the player is not prepared by the first encounter with the Dragon Zombie, the skill could be lost forever.