Great Sword = 2d6 + 5
Great Weapon Master Feat = + 10

Lvl 5 Oath of Vengeance Paladin‘s Divine Smite = 5d8 and Branding Smite = 2d6
Lvl 8 War Domain Cleric‘s adds more spells slots for more divine smites and it’s Divine Strike = 1d8
Lvl 3 Battle Master Fighter grants Action Surge to 2 more attacks and Superiority Dice = 4d8
Lvl 3 Hunter Ranger gives Colossus Slayer = 1d8
Lvl 1 Rogue for sneak attack = 1d6

Across 4 attacks with action surge that translates to: 17d6 + 27d8 + 60!!!

Attack 1 of 4 with action surge

(5d6 + 11d8 + 15) = Max damage 133

Attack 2 of 4

(4d6 + 6d8 + 15) = Max damage 87

Attack 3 of 4

(4d6 + 5d8 + 15) = Max damage 79

Attack 4 of 4

(4d6 + 5d8 + 15) = Max damage 79

Total for 1 turn = 378