Master Assassin (5e Optimized Character Build)
From D&D Wiki
Do you love dealing massive damage, do you hate long fights, do you want to be able to kill a young dragon in one round at level 10? Then this is the build for you.
Warning; This build is heavily multiclassed, it only has one ability score improvement and is only effective once per day and if hidden.
The core classes are;
Total level 10
When you get level 3 Rogue pick the Assassin Subclass for the autocrits in the surprise round
Get 5 levels in Fighter for action surge for the extra action and bonus action and for two attacks per Attack action
Get 1 level in Cleric, pick the War domain and have 14 Wisdom for using bonus actions to make a single attack
Get 1 level in Warlock for the hex spell for an extra 2d6 damage per attack
Use a rapier and get the dueling fighting style to deal 2d8 + 2 per attack and be able to use sneak attack once (4d6)
Have 20 Dexterity for +5 damage per attack
So now you cast hex on your target while sneaking up to them (use fly and invisibility for guaranteed success) and assuming every attack hits you deal 12d8 + 16d6 + 42 which on average is 152 damage !!!
You also have advantage on every attack, all of this at level 10
Be a Half-Orc for savage attacks to add 6d8 (+27) to the normal build or use the Barbarian variant with a greataxe instead of a greatsword for +6d12 (+39) and great weapon fighting style will add another 5 on average.
Get 3 levels in Barbarian (pick path of the berserker) instead of 1 level in Cleric and Warlock
Use a greatsword and get the great weapon fighting style
Have 20 str, don't care about dex or wis
You lose sneak attack, duelling and Hex but you gain rage damage that replaces duelling, more damage from the greatsword and you can reroll all of the 1's and 2's on your damage.
Your damage becomes 24d6 + 42 averaging 126 before you do your rerolling. Averaging 142 with rerolling.
Get to 9 levels in Barbarian and only have 2 levels in Fighter for brutal critical and more rage damage and swap the greatsword for a greataxe to deal 18d12 + 48 averaging 165 before you reroll. Averaging 180 with rerolling.
Divine Smite Variant
Get 2 levels in Paladin and lots of spell slots for Divine Smite
For those that don't know Divine Smite, it is a level 2 paladin ability where you can expand a spell slot to add (the spell slot level + 1)d8 damage to an attack, the damage is also doubled by crits, the damage maxes with a 4th level spell slot so you need 11 spellcaster levels to get the maximum damage for 6 attacks which is +60d8.
So if you get;
3 Rogue, 1 Cleric, 2 Paladin and
1 warlock, 5 or 6 Fighter (Eldritch Knight) or
5 or 6 Ranger, 2 or 3 Fighter (Eldritch Knight) and
then get to level 20 with Bard, Cleric, Druid, Sorcerer or Wizard then you can deal 72d8 + 16d6 + 42 averaging 422
If you get level 3 Fighter pick Battle Master for your archetype and the precision attack maneuver for +1d8 on 4 attack rolls and if the attack will hit without the +1d8 to hit you can use it to add 2d8 to the damage using some other attack maneuver like trip and menacing which will half their speed next turn and prevent them from moving closer to you (if they fail their saving throws) so if after attacking you move back 5ft they can't hit you with melee attacks and unless they have 60ft speed they can't get away from you. Do keep in mind if you then go for Divine Smite variant then you will have 1 less spellcasting level as that comes from the Eldritch Knight archetype so you will deal 2d8 less damage on your 6th successful attack.
Get another level in cleric for +10 on one attack roll.
Get 2 levels in Wizard and pick divination school to get the portant feature which can guarantee 2 attacks.
Instead of 1 level in Warlock you can get 2 levels in Ranger and have Hunter's Mark instead of Hex for the same effect.
If you get to level 3 Ranger pick the Hunter archetype’s colossus slayer ability for +2d8.
Also if you get the revised ranger and you are attacking your favoured enemy then you get +12 damage and attacking your greater favoured enemy adds 24 damage.
The sorcerers empower meta magic can apply to the damage from the hex spell, so if you have 14 Cha and have 3-6 levels in sorcerer you can reroll 3-6 of hex's 2d6 damage
You can also get Extra Attack from Paladin, Ranger and Warlock instead of Fighter but that adds levels to the build.
Ask your DM if you can make an Eldritch invocation that lets you cast Hex and Hunter's Mark as one spell using a spell slot as an action once per long rest for an extra 12d6 damage.
If your DM is agreeable ask if you can fall onto your target to deal damage. The idea would be to get above your target, fall and make an attack roll to land on them which if you succeed they also take your fall damage and the attack and damage rolls are affected by the assassinate feature. But regardless of the outcome you still take your fall damage.
Variants from Unearthed Arcana
There is a big change if you can use Unearthed Arcana and that is the Curse Bringer Eldritch Invocation, which is like Divine Smite but better because it is 2d8 per spell level without a damage limit. This requires you to have 3 levels in Warlock and pick the Hexblade Parton and the Pact of the Blade, which gives you the added benefits of cursing someone as a bonus action so you can add you proficiency modifier to damage rolls and you can use Cha instead of Str/Dex for weapon attacks. Also at warlock level five you can get Thirsting Blade which is Extra Attack so you don't need to get to fighter level 5.
This means the level 20 build is 5 Warlock, 3 Rogue (Assassin), 1 Cleric (War), 3 Fighter (Battle Master) and 8 in full spellcaster classes
You can take the Monster Hunter fighter subclass instead of Battle Master for almost the same effect.
If you get 2 levels in Druid and pick the Circle of Spores you add 2d6 damage per attack and you can use your reaction to deal 6 damage, this requires you to take an action at most a minute before you make you attack, then if you get to level 6 your reaction deals 12 damage and if you kill a creature with that 12 damage then the creature becomes a zombie for you.
If you get 3 levels in Bard and pick the college of whispers you can add 4d6 damage, then if you get to level 5 you can add an additional 2d6 damage
If you get 1 level in Sorcerer and pick the Divine Soul subclass you can add 2d4 to an attack roll after it fails
Your first level should be Warlock and you should fight by casting hex and dual wielding daggers this lets you deal 2d4 + 2d6, and you can do this at 20ft as daggers are really cheap so you can buy lots and throw them around with impunity.
Then get 2 levels in fighter, 3 levels in rogue and dual wield short swords to deal 6d6 without action surge or autocrits, 20d6 with them
(Spellcaster levels is your Bard + Cleric + Druid + Sorcerer + wizard + 1/2 Paladin + 1/2 Ranger + 1/3 Arcane Trickster +1/3 Eldritch Knight levels)
(The great weapon fighting style adds (D-2)/D damage on average per dice where D is the dice size. e.g. D is 12 for d12’s which with great weapon fighting style adds ⅚ of a point of damage on average)
Note; If you are somewhere you are not allowed to be armed such as a royal castle and you want to assassinate someone, this build with the Warlock Pact of the Blade is perfect.