From the Super Mario Wiki
Strong Greenies are a variation of Greenies in Luigi's Mansion: Dark Moon that have been powered up by a special crystal from the mines, giving them a cracked appearance. Their first appearance in the Dark Moon Quest mode is in the fourth world of the game, Secret Mine. Strong Greenies have 50 HP. Just as normal Greenies, they can equip objects and use them to attack, they can also attack in groups. Luigi can use to dodge the other's attack while sucking one up. Strong Greenies escape from their crystals by punching through them, almost breaking the crystal.
Ghost Container description
The Crystals of the mine have really changed these charming fellows. They're now much stronger and more able to get into shenanigans. Don't let them get equipped!
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