Zardnaar
Legend
I took a guess. It is a Longsword wielded in 2 hands - 2 attacks, plus Truestrike. So it is like 3d10 sword + 6d6 vicious + 3d6 truestrike + 15. Probably.
Fighter has Greeat Weapon Master, and is attuned to both a Hammer of Thunderbolts and a Belt of Giant Strength, giving him an extemely high strength, I am guessing its around 28.
He also usually rolls with advantage due to topple, which enemies usually fail and crits on an 18.
If you add in his crit range with advantage, a +6 for GWM strength it is over 30 per hit. On average he usually doing about 200 damage if he action surges. This I do know. The last fight had a lot going on and it is possible some of those guys took damage from AOEs. The other 3 fights I am pretty confident about.
It is action economy.
In the first fight THL made it so 3 enemies, all who got a turn, had a total of 1 action ... and it would have been 0 actions if the third enemy was visible when I cast the spell.
In the boss fight, the boss got 2 turns. The other 3 non-minions got around 10 turns between them in 4 rounds but they only got to take 3 actions out of those turns. So lets say Tasha's hideeous laghter took away 6 turns from the enemy, and whatever the Bard cast took away one.
This is in addition to making them prone so the Fighter (and the rest of us) attacked with advantage.
THL is also much better at high level when your DC is near impossible for someone without proficency and even more so when they are rolling with disadvantage.
Given the performance of THL in this adventure, I would argue upcast at 5th level is substantially better than Hold Monster.
They take the Dash action every turn, so they can not take other actions. This is how it was in 3E as well. It is not like turn undead where they can take another action if they can't move any further.
Sorry if I was not clear on that.
THL is?