Whimsicott: 60/67/85/77/75/116, BST: 480
Eldegoss: 60/70/80/110/100/65, BST: 485
Eldegoss is essentially the same Pokémon as Whimsicott, but more defensively oriented. It has 5 more BST due to recent power creep, which will be the theme for the rest of the list.
Carracosta: 74/108/133/83/65/32, BST: 485
Dreadnaw: 70/120/100/60/90/50, BST: 490
Gigantamax Dreadnaw: 70/145(+25)/150(+50)/70(+10))/115(+25)/40(-10), BST: 590
Dreadnaw is physically oriented exclusively, unlike Carracosta, and unlike it, it has an actual Speed that can work with Shell Smash. Gigantamax Dreadnaw is given Mega-like stats (+100 BST boost), like the other Gigantamax forms here will be given.
Talonflame: 78/81/71/74/69/126, BST: 499
Corviknight: 80/100/110/60/85/70, BST: 500
Gigantamax Corviknight: 80/130(+30)/140(+30)/60(--)/115(+30)/80(+10), BST: 600
Corviknight due to its sheer size and weight finally crashes the 500 BST ceiling, but fails to make much head. Due to its BST limitation, it will need its Gigantamax Form to unleash its true power.
Swirlix: 82/80/86/85/75/72, BST: 480
Alcremie: 75/60/72/108/100/70, BST: 485
Gigantamax Alcremie: 75/60(--)/107(+35)/138(+30)/135(+35)/70(--), BST: 585
Alcremie is a min-maxed Swirlix essentially. Due to its gimmick it doesn't have a substantially high BST.
Pallosand: 85/75/110/100/75/35, BST: 480
Polteageist: 50/55/125/110/95/55, BST: 490
Polteageist does not seem to have a Gigantamax form for now, so I gave it more generous stats. It is still weaker than Gengar, obviously, as it is only two-stages. Because it is tiny, its HP is incredibly low.