The 12 Days of Critmas: The Cleric
Clerics are the most powerful class in dungeons and dragons :(
There are so many cleric subclasses, which are all really different and mostly really good. For dealing loads of damage, we can pretty quickly rule out the trickery, twilight, order, peace, life and knowledge domains. These don’t add any new damage options to the base class, beyond divine strike or potent spellcasting, which every subclass gets. The rest of the cleric subclasses can again be split into weapons and spell people. In the first camp, we have the death, forge, tempest and war domains; in the second, nature, light, grave and arcana. I’ll group ones with similar approaches together, so it hopefully doesn’t get too confusing. For most of these subclasses, their highest damage spell is upcast inflict wounds, which deals 6d10 on a melee spell attack, and can, importantly, crit.
The forge cleric doesn’t get proficiency with martial weapons. It can, however, make its weapon +1 with blessing of the forge and cast spells such as bestow curse and elemental weapon to improve the damage dealt by its weapon attacks. For maximum damage, our cleric will want to hit with their weapon and divine strike, possibly using a melee weapon cantrip, then use Metamagic Adept to cast inflict wounds with their bonus action. This will mean dropping concentration on whatever spell is improving their damage output, but that’s fine. We’re left with one feat slot. The main options seem to be Orcish Fury, GWM and some way to pick up a heavy weapon proficiency, or Magic Initiate for a cantrip such as booming blade. Let’s weigh these up. The Orcish Fury build will do 41 (1d12 +1d12 +1 +1d8 +1d8) with their action. The GWM will also do 41 (1d12 +3 +10 +1d8 +1d8), also with an action, and the Magic Initiate will do 37 (1d12 +1 +1d8 +1d8 +1d8) which increases to 53 if the bonus damage is triggered. These all increase by 60 with the bonus action spell, so all of these builds work out to pretty much the same, 100 ish damage. A high elf can learn booming blade for free, and has proficiency with longswords, so can also deal 41 damage with their action (1d10 +3 +1d8 +1d8 +1d8) with a spare feat. Using Martial Adept, they can therefore increase their base damage to 103, with a maximum of 119. This seems to be the optimal forge cleric for the purpose of killing something in a single turn.
Death and tempest clerics get martial weapons proficiency for free, and can both use divine strike. Death clerics’ other important considerations are that they can deal an extra 21 necrotic on a melee hit twice between rests and know the spell blight, which deals 8d8 damage. Tempest clerics can cast call lightning at 4th level for a maximum 5d10 damage in a turn, and have some cool other abilities, but these don’t increase damage, so the death cleric will do more with the rest of the build the same. With free weapons proficiency, and assuming we take Metamagic Adept to cast blight as a bonus action, it’s likely the variant human or half-orc will be best here. Let’s say both have bestow curse running, and hit using divine strike and touch of death (the 21 damage). A half-orc with Orcish Fury will deal 63 on a hit (1d12 +2 + 1d12 + 1d8 +1d8 +21). A human with GWM and Martial Adept will do 67 (1d12 +2 +10 +1d6 +1d8 +1d8 +21), narrowly beating them. A human with GWM and Magic Initiate for booming blade will do 69 (1d12 +2 +10 +1d8 +1d8 +1d8 +21), up to 83 if the extra damage is triggered. The total for our human, including the quickened blight, is 133, without crits or extra booming blade damage. If those were nat 20s, they’d deal 169 damage, 185 if booming blade is triggered, which beats the half-orc's extra crit damage from savage attacks by 2 points. However, you can't crit on blight. If they quicken inflict wounds instead and crit, maximum damage is 255, or 241 with booming blade set off.
It seems unlikely any of the spellcaster subclasses will beat this. The nature cleric gets a druid cantrip, divine strike, and their best damage spell is up-cast inflict wounds for 6d10 damage. Sadly, shillelagh can’t beat a greataxe for max damage (1d12 vs 1d8+3), so with our usual formula they won’t beat the death cleric, who is proficient in this weapon, deals a load more extra damage on melee hit, and has a higher damage spell to quicken on their bonus action. Arcana clerics gets two wizard cantrips (booming blade timeee), and can add their wisdom modifier to cleric cantrip damage. So without feats, a greataxe proficient arcana cleric’s damage on an action when bestow curse is up is 33 (1d12 +2 +3 +1d8 +1d8). It doesn’t really compare to the death cleric. Light clerics can cast fireball at 4th level, but 9d6 still doesn’t beat inflict wound’s 6d10 on a single target. They won’t be catching up either.
The last hope for spellcaster clerics is the grave cleric. They can cast blight, but won’t need to do so for huge amounts of damage, thanks to their channel divinity option, path to the grave. This lets them curse a creature until the end of their next turn, who then has vulnerability to all of that attack’s damage the next time they are hit with an attack. This means they take double damage, which is pretty insane. If we did path to the grave and our quickened spell on one turn, it would be 120 damage in a round, so completely nuts. But as this whole series is kinda bs, we’ll say our cleric cursed their enemy last round. They then quicken 4th level inflict wounds, dealing the crazy 120 damage, and still have an action. An elf with booming blade and a longsword proficiency for free, and GWM, will do 30 (1d10 +2 +10 +1d8) base damage, which isn’t matched by GWM and greataxe proficiency, or a half-orc with Orcish Fury. The total in a round, with bestow curse running as well, is therefore 158 (12d10 +1d10 +2 +10 +1d8 +1d8), which is genuinely insane. Now imagine this all crits. 12d10 becomes 24d10. The total is 296 (24d10 +2d10 +2 +10 +2d8 +1d8), increasing to 312 if the target is still alive after all that and runs away, triggering booming blade.
I’ve basically been immediately proven wrong. The grave cleric is terrifying, and while it’s unlikely you’d ever roll max damage, path to the grave is still unbelievably powerful. I’m not sure if anything will beat this build for damage in a single round of combat, but there’s 9 days to go and given my lack of success predicting so far, I’m probably completely wrong.