I thought about it and I think we should let him have that one
I know it makes no sense and makes Law look weak, but, it makes Blackbeard look like a borderline god tier since Big Mom couldn't put Law down for good with tens or hundreds of attacks (plus an attack from Hybrid Kaido and also one from Zeus prior to their fight) while BB supposedly only needed one to win (besides the legendary submarine that, as scholars like Erkan admit, needed a lot of Quake punches to defeat)
Yeah, I don't think Teach can beat Kaido in a 1v1 (yet, IMO he's close), but I think Teach mid/high diffs Linlin.
Linlin isn't completely Fruit based, but it's a lot of her arsenal.
Teach has enough Haki to scar Shanks, a guy who learned Kamusari at... 15?
Teach's greatest feat IMO is managing to hide his true power all this time. Even AFTER becoming a Yonkou, he's been hiding his true strength for the perfect moment.
Haki is Will based, and Teach is BY FAR one of the most ambitious/prideful characters in the series.
We know from Kaido that Haki is the most important power, surpassing the Magical Science of Devil Fruits, and whatever Magic the Gorosei/Imu are using; we know this also from Joy Boy's Rope Haki Infusion ruining the Gorosei's days.
Teach is a Haki Merchant masquerading as a Devil Fruit merchant, IMO, he's just a total problem.
Hell, we've never seen Teach use his Tekko-Kagi blades, what Teach used to scar Shanks, in a real fight. Teach also takes twice the physical damage, so, IMO, this is why we haven't seen him use his Tekko-Kagi in serious fights; Teach only uses them when he's willing to risk taking a lot of physical damage against serious opponents.
When Teach has both Tekko-Kagi coated in Color of the Supreme King, we'll know it's Serious Teach. I also think his claws are a reference to him having the Kraken Fruit: Tekko-Kagi rhymes with Takoyaki.
Teach's Tekko-Kagi has 4 blades: now that he uses two, rather than one, that's 8 blades. 8 Blades = Octopus = Kraken