Class for fighting mutiple enemies

Was making up a new character and wanted to know the best class for single combat against multiple enemies or If there was an archetype specifically designed for that

Polearm Fighter, or any reach-build with Combat Reflexes and a couple of trip related feats can do a lot of harm to many opponents.

Master of Many Style Monk archetype can mix up a couple of style feat chains to give themselves reach and shorten the path to Whirlwind Attacking. My friend's got a specific build that combines Dragon and Marid Styles.

Literally anybody with Cleave and related feats, though they lose their luster over time so a Fighter who can retrain them gets a leg up.

That very much depends on what level you are talking about. Low level favours reach weapon users, ideally ones who can also increase their size. Longspear wielding clerics or oracles with enlarge person via Domain or Mystery. Alternatively any pet class such as the Druid. Colour Spray users can do well but only a few times per day at low levels.

At mid levels (6+) then the advantage swings to the primary casters. Glitterdust, Stinking Cloud, Slow, Confusion etc all wreak havoc on groups of enemies. Heavens Oracles similarly do so with Widened Colour Spray which continues to be effective due to their revelation.

At high levels (15+) then groups of enemies is all about the casters. There is nothing much better to deal with a dozen angry monsters than a spell perfected dazing chain lightning or a persistent Holy Word with a nigh unbeatable DC which tears through SR like it wasn't there.

Look at the Whirlwind Attack feat. A fighter can get it at level 4 (through retraining), so you can have cleave earlier and leave it behind at 4th. This with a reach weapon and a potion of enlarge person gives you 36 squares you can attack, and more if you are allowed a five-foot step in the middle of the full-round action.

Personally, I love paladins, as their survivability is huge. It will take longer to put down a horde than with the fighter above, but they can keep going for a longer time, and have much better defenses against magic and spell-like abilities.

I agree with the comments above. Combat Reflexes, DX12+, and a reach weapon are ideal for fighting multiple opponents. Note that the longspear is a simple weapon, so most character classes have access to it. There are also various advanced feats that help with this (e.g. cleave, whirlwind). Just having Combat Reflexes, DX12+, and reach will take you far vs. multiple foes.

At higher levels spells become more effective than weapons at defeating multiple foes.

Specializing in boom spells can put you at ridiculous levels even at lower levels.

1 level in Crossblooded Draconic/Orc Tattooed Sorcerer gets you a Burning Hands that deals 2d4+4 damage.

The rest goes into Admixture Wizard for blasting goodness. You even get Spell Focus(Evo) for free if you play in PFS.

Level 3 gets us Spell Specialization and puts our Burning Hands at 5d4+10 damage.

Take Intensify Spell and that Burning Hands goes a long way capping at 10d4+20 damage. At 6th level if you grabbed Bloatmage Initiate.

Lunge+ cleave and greater cleave?

Spell caster with AoE spells. No marshal is going to be able to deal with that many enemies in one round.

If the enemies are evil, then Paladin. Get smite up on as many as you can, and your defenses will be strong, while you start taking them out.

Alchemist. Because: BOMBS!

A negative energy channeler seems a decent option too!