The Meat Man is the most durable monster in the game, with enormous sums of hit points, but limited by poor attack damage. The key weakness of the Meat Man is his health regeneration; although he has a massive hit point total, he does not heal any faster than regular monsters. Since the damage he deals on each attack is rather low, it can be quite easy to simply fight him by attrition by healing between blows. Characters with resistances or very high damage output, such as the Rogue, Paladin, or Monk can slaughter Meat Men with ease. Physical resistance and high attack damage are the best attributes to focus on when fighting meatmen.
Anyone using the APHEELSIK glyph can whittle these low-damage behemoths down to size in a very cost-effective manner. The healing glyph HALPMEH is a close second against this monster, since you don't need to spend very much mana to cure the relatively minor wounds it delivers. Glyphs that deal direct damage, such as BURNDAYRAZ or PISORF, are highly ineffective, as are one-time buffs such as ENDISWAL, GETINDARE or CYDSTEPP.
Meat Men can be difficult to fight if you're out of exploration space, since their primary weakness is their slow health regeneration. That doesn't mean anything if you can't explore new tiles to heal yourself. As a result, it's always better to deal with Meat Men as early as possible.
If you have Life steal (from a Vampiric Blade, Dracul, or being a Vampire), Meat Men are a fantastic target. Because of their low damage, you will heal for a significant portion of the damage that you take every hit. For Vampires, Meat Men are ideal "blood cows" - hit them to heal (but don't kill them) and explore to let them regenerate health.
When tackling the Super Meat Man boss, you will want to begin the boss battle early so you can explore and maintain a long battle of attrition. If possible, worship Tikki Tooki to gain his poison boon, or use the APHEELSIK glyph. Otherwise, your best bet is to focus on boosting your resistances and attack damage and beating this boss by sheer attrition.