Let us build a single creature ground and pounder!

[Chryssis]

you could do a jumpy version: a tabaxi, monk 4 (pick your favorite subclass), Thief 3, Champion 7 (dueling style), Totem Barb 6 (spirit tiger, aspect bear), for maximum oomph. Belt of storm giant strength, boots of striding and springing, ring of jumping. Transmutation stone (10ft speed), potion of haste, someone to cast longstrider and enlarge on you (not required but more fun). Mobile and Althete feats.

This results in you being Capable of jumping 388 feet straight up by yourself, or just the 200ft required to hurt someone. you have +21 and advantage on your athletics check. you can sneak attack with a dagger (or rapier but seems a little wierd) for 1d4+13 +2d6 with crit on 19/20. or just punch them for 1d4+11 grapple and jump 200ft in the air. they will take 20d6 and be proned. you will take 20d6 -20 unless you can figure a way to get feather fall (ring of feather falling instead of jumping, and a friend to cast jump on you, or if you are using the potion of haste take magic initiate instead of mobile feat to get jump yourself)

 

[BookBarbarian]

Is UA on the table?

A Scout Fighter with Prodigy will have expertise in Athletics, and can add Half a Superiority Die roll to Athletics checks. Rage, and Enlarge both provide Advantage on Athletics checks, but only the latter will allow you to help grapple Huge creatures.

Scout Fighter 5/(any) Bard 3 will get everything you need.

Edit: Oh and remember no matter how good you are at grappling, some creatures are just flat out immune to being grappled, like the Water Weird. So the next most important decision is "What do you want to do when you can't grapple?"

 

[Slit518]

Is UA on the table?

A Scout Fighter with Prodigy will have expertise in Athletics, and can add Half a Superiority Die roll to Athletics checks. Rage, and Enlarge both provide Advantage on Athletics checks, but only the latter will allow you to help grapple Huge creatures.

Scout Fighter 5/(any) Bard 3 will get everything you need.

Edit: Oh and remember no matter how good you are at grappling, some creatures are just flat out immune to being grappled, like the Water Weird. So the next most important decision is "What do you want to do when you can't grapple?"

If I can't grapple it, learn how to grapple it!

Get Ice Mitts, grapple the Water Weird!

 

[ZenBear]

One of my players is a Luchador Rogue. Homebrew Wrestler subclass that grants at level 3 the option to use Cunning Action to attack a foe you have grappled. Works pretty well, if not 100% optimized.