Sabertooth skull shape convergent evolution over the years (and tree of life). A brilliant example of (at least superficial) iterative phenotypic convergence.
Only one of these belongs to a cat, and one of them isn't even a 'proper' mammal!

(A) gorgonopsid Smilesaurus ferox, (B) sparassodont Thylacosmilus atrox, (C) creodont Machaeroides eothen, (D) nimravid Hoplophoneus occidentalis, (E) barbourofelid Barbourofelis fricki, and (F) felid Smilodon populator - the only cat!

Smilesaurus is a stem-mammal; a group closely related to but not actually within mammals.

Thylacosmilus is a sparassodont, a non-marsupial metatherian; again, closely related to but not actually within marsupials.

Machaeroides is a creodont, maybe an oxyaenid creodont... but it's difficult. Creodonts were (ready for it?) non-carnivoran carnivorous mammals. Yep you read that right. A lot of the big mammal groups are unhelpfully named...

...like Carnivora, which includes the plant-eating (herbivorous) panda and not the animal-eating (carnivorous) shrews or toothed whales.

Hoplophoneus and Barbourofelis, nimravid and barbourofelid respectively, are both feliforms, like cats, hyaenas, and mongooses. Barbourofelids are probably very closely related to cats (maybe even the sister group), but nimravids probably much more distantly related to the whole.

And everyone knows good ol' Smilodon, the most boringest of sabertooths. At least I didn't pick S. fatalis, right?

S. populator is pretty weird - almost a cat wearing a bear suit. Not hugely normal of the group, to be honest...