Hold Person or Hold Monster to Paralyze the enemy ensures every hit is an auto-crit, which will both ensure they don't miss and will double the damage dice involved. An Oathbreaker Paladin as an ally with Crusader's Mantle and Aura of Hate can also improve the damage. If you're willing to MC into Spore Druid you can get Haste Spores on all of those with Armor of the Sporekeeper, doubling the number of attacks.
All those things combined, which admittedly requires an ally, a Multiclass, and a failed save on Hold Person / Hold Monster, and you'd be looking at:
8*37(rounding 6d6+2d4(crit, crusaders mantle)+3(str)+4(pro)+4(cha if 18)) + 8*24(6d4(crit, crsaders mantle)+1(str)+4(pro)+4(Cha)) = 296+192 = 488 damage. And honestly it's far more likely this way, as them failing a Hold Person / Hold Monster is all that's required, and then the rest of it is guaranteed. Plus a paralyzed enemy isn't going to kill the summons with an AOE effect. Remove the Paladin and you're taking away 144 damage from that but you're still at 344, well over the 200 you were looking for.
Not sure what build you were thinking in general but you only need 2 levels of Druid to pull off the spores, though a Wis 6 / Druid 6 gets the Fungal Zombies as well, not only providing more damage but also applying a condition to enemies causing them to raise as zombies in turn, potentially getting your little army to spiral out of control. As Draganta pointed out though the reality will likely be underwhelming compared to the theoretical damage associated with it, but CC which provides advantage will help bridge that gap a bit, and paralysis is as obscenely powerful as ever.