From the Super Mario Wiki
A Jinx Clone is a monster that Magikoopa can summon in the game Super Mario RPG: Legend of the Seven Stars. The enemy is a clone of Jinx, the master martial artist of Monstro Town. The Jinx Clone is one of three creatures that the Smithy Gang's brainwashed Magikoopa manifests during his battle with Mario's party in Bowser's Keep; the other two monsters are Bahamutt and King Bomb. Like these other summoned monsters, a Jinx Clone hatches from a strange Yoshi Egg after Magikoopa casts a magic spell on the egg. When a Jinx Clone is present, Mario and his party can not attack Magikoopa until the summoned creature is defeated. A Jinx Clone has the same appearance as Jinx, and these copies know many of the original's powerful fighting moves, including Jinxed, Quicksilver, Triple Kick, and Silver Bullet.
Overall, Jinx Clones are relatively weaker than Jinx himself, although in some regards they surpass Jinx's original, less powerful form (the first of three forms). A Jinx Clone has significantly less HP and magic defense than Jinx (in any of his three forms). On the other hand, a Jinx Clone's defense is even with Jinx's second (middle) form, and the monster actually has the same amount of attack power as Jinx's most powerful form.