Best class killers

[Vulgosh]

I want to know what monsters/ other things you can think of kill a certain class the easiest (like what kills a wizard the easiest).

[Lord Tataraus]

Living Greater Dispel Magic

[blue_fenix]

Generally speaking, although a lot of players cover these weaknesses with specific feats and magic items:

Wizard/Sorcerror: Damage, grapples, sundered spell book / component pouch, anything they don't have time to prepare for, anti-magic field. Wizards are best slain with ambushes. Unless they have contingency, in which case it can be hard to kill them at all.

Cleric/Druid: Nothing in particular, these are the most versatile classes in the PHB.

Fighter: Anything that requires will saves.

Rogue: Undead, golems, etc. immune to sneak attack. Anti-magic fields and spell resistance against UMD rogues.

Monks: Anything it can't reach, e.g. a flying enemy with ranged attacks/spells.

Paladin: Moral connundrums. Should I kill the baby? I mean, he's the anti-christ and all, but he's just so cute!

Barbarian: Books. No, seriously though, will saves, though not as bad as fighter. Also, see monk.

Bard: See cleric/druid, except bard is weaker, so easier to kill in general.

[Wraithy]

you could cheat

[Telonius]

This is really too broad of a question to answer sufficiently. There's a lot of variation within a class, both in terms of feats and equipment chosen, and level. A rust monster might mop the floor with one particular fighter build, but get owned by a fighter with a quarterstaff. A Golem might obliterate one wizard, but have problems against another.

That said, Fighters tend to have problems with anything that deals a touch attack. Monks have big problems with flying enemies. Bards have problems with mindless foes. Rogues tend to have it tough against undead, plants, and anything else immune to sneak attack. Wizards have problems with clerics, druids, and other wizards. Same way with clerics and druids. Everybody has problems against That Damn Crab.

[Kyeudo]

Fiendish Sentry Ooze Living Mordenkainen's Disjunction Monk 2.
Kills anyone dependant on gear.
Does not require gear.
Has Wisdom out the wazoo and decent saves.
Is smart enough to use tactics.
Has SR to deal with any spellcasters.
Has DR that, once it lands a few hits, can't be bypassed.

If I calculate the CR correctly, it also comes to a CR of 22.

[PlatinumJester]

Powergaming

Warblade with Diamond Mind Maneuvers.

[Fax Celestis]

Any creature with more than 10 HD and the Paragon and Spellwarped templates. Too tough for fighters, too high of SR for casters to break...and they absorb spells that don't pass their SR and get stronger.

[Zim]

Huge fiendish monstrous crab. I understand that these are very hard to deal with.

I personally like pyrohydras. Though not unkillable, they are waaaay mean and the fast healing keeps them ticking for a goodly time. Nice high challenge for low levels.

[Mewtarthio]

Fiendish Sentry Ooze Living Mordenkainen's Disjunction Monk 2.
Kills anyone dependant on gear.
Does not require gear.
Has Wisdom out the wazoo and decent saves.
Is smart enough to use tactics.
Has SR to deal with any spellcasters.
Has DR that, once it lands a few hits, can't be bypassed.

If I calculate the CR correctly, it also comes to a CR of 22.

"Sentry Ooze"? What's that from, and what's it supposed to do? I'm picturing a guy who has Gelataneous Cubes guarding his castle.

Also, technically, shouldn't a Living Disjunction be immune to spells? It would just disjoin anything that hit it. Regrettably, a Living Disjunction is most often defeated by clever players who viciously attack the source of its power: The sadistic DM.

[Fax Celestis]

Try applying Paragon to That Damn Crab, too.

PARAGON ADVANCED HUGE MONSTROUS CRAB (CR 23)

Spoiler

Show

N Huge vermin (aquatic)
Init +8; Senses darkvision 60 ft., low-light vision, scent, Listen +18, Spot +22
AC 59, touch 40, flat-footed 51
hp 355 (16 HD)
Immune mind-affecting effects
Resist fire 10, cold 10, damage reduction 10/epic, spell resistance 48
Fort +29, Ref +23, Will +23
Spd 90 ft. (18 squares)
Melee epic claw +52 (2d6+35) or
Melee 2 epic claws +52 (2d6+35)
Space 15 ft.; Reach 15 ft.
Base Atk +12; Grp +45
Atk Options constrict 4d6+35, improved grab
Abilities Str 41, Dex 26, Con 29, Int —, Wis 26, Cha 17
SQ amphibious, fast healing 20
Feats Toughness^B
Skills Hide +14, Spot +22

Amphibious (Ex): Although an advanced Huge monstrous crab is aquatic, it can survive indefinitely on land.

Constrict (Ex): An advanced Huge monstrous crab deals damage equal to twice its normal claw damage plus its Strength bonus on a successful grapple check.

Improved Grab (Ex): To use this ability, an advanced Huge monstrous crab must hit with a claw attack. It can then attempt to start a grapple with a +13 bonus as a free action without provoking attacks of opportunity. If it wins the grapple check, it establishes a hold and can constrict.

[Lord Tataraus]

"Sentry Ooze"? What's that from, and what's it supposed to do? I'm picturing a guy who has Gelataneous Cubes guarding his castle.

Also, technically, shouldn't a Living Disjunction be immune to spells? It would just disjoin anything that hit it. Regrettably, a Living Disjunction is most often defeated by clever players who viciously attack the source of its power: The sadistic DM.

By RAW, no it would not be immune to spells. I did consider posting the Living Disjunction, but I decided to answer specifically to the "(like what kills a wizard the easiest)" part. I figured a Living Greater Dispel Magic would counter every spell thrown at it and dispel all of the wizard's buffs all while grappling. Of course to be safe you could make it a Fiendish Sentry Ooze Living Mordenkainen's Disjunction Greater Dispel Magic Monk 2. Or even a Fiendish Sentry Ooze Living Mordenkainen's Disjunction Greater Dispel Magic Wail of the Banshee Earthquake Monk 2 try to survive that! (all completely legal by RAW, except WoB depending on your interpretation)

Sentry Oozes are awesome! (You got it right by the way) It is a template in Dungeonscape that makes an Ooze intelligent in addition to a bunch of other buffs to enhance its guardian abilities.