Mack was ordered to attack the Mushroom Kingdom and occupy it for Smithy. A number of Shysters were hired from the 8 Bits Club to assist Mack, and since he shared the Shysters' passion for bouncing, they quickly accepted him as their leader.
As one of Smithy's leiutenants, Mack is quite powerful, and he has a powerful command of fire magic. Some believe that he should be classified as a fire type because of this, but he also has features of human and plant-type characters, and has finally been classified simply as a "monster".
"As the old Mushroom Kingdom saying has it, the plumber is mightier than the sword. Unleash Mallow's Thunderbolt on the squads of Shysters guarding Mack while Mario Jump Attacks the ringleader. Mario shouldn't attack the minions and Mallow should lay off Mack." - SMRPG Player's Guide.
"Boing, boing, boing." -SMRPG
(To Shyguys) "Listen up, gang! These guys are gonna put a stop to OUR party! Are we happy about this?!" - SMRPG
Attack Pattern: He mainly uses fireball (which hits one character and causes about five damage) and firewall (which hits both characters, but causes only about two points of damage). He also attacks directly once in a while, and sometimes he'll do a big jump off the screen for a period of time.
Basic Strategies: The strategy put forth in the "other info" section works fairly well. Mario should use Jump (Super Jump if you've got it) on Mack, while Mallow uses Thunder on all enemies (it causes quite a bit of damage to Mack, too.)
If there are no Shysters to fight, Mallow can cause a fair amount of damage to Mack with his regular attack. You might also want to consider using him to restore HP and FP if they are low.
Advanced Strategies: Mack hardly ever does regular attacks, but if he does, try to press A just before he hits you. When he jumps, you'd expect him to come back down on your heads, but he doesn't. Even so, it might be a good time to refuel, since he doesn't return until you beat all remaining Shysters.
I mentioned Super Jumps in the Basic Strategies. I believe you get this technique at level 6 (maybe 5), and it makes it quite easy to beat Mack. Four of them, if properly timed, will probably be enough to take him out. To conserve FP, use two and finish him off with Thunder attacks from Mallow and regular attacks from Mario.
