A friend and I have been trying for about an hour to remember what character we're thinking of. Morse, from Balto, reminded us.
It's his underbite, with the way the lip comes to a point, the teeth sticking out, and the bug eyes. We think it was either a dog or a fish. Kyle, from Despicable Me, is pretty close, but has too many teeth and his mouth is too round - we also think it was 2d animation.
The pike from Sword in the Stone is likewise similar, with the underbite and pointy teeth, but his jaw is too long, and we think it was more of a comedic relief character than the pike.
Overall, the character was more comic relief; we think it went around biting people a lot or something for comedic effect. No talking. Anybody have any ideas?
Here’s an extremely specific answer: could it be the giant dog at the start of the Chuck Jones-produced Tom & Jerry short Purr-chance To Dream (1967, on Wikipedia)?
More generally, the drawing you posted reminded me of the drawing style used to draw dogs on Tom & Jerry when Chuck Jones was producing, and this was the best example I could find quickly. I suspect there’s others, possibly playing a more prominent role in their story, which you might be thinking of!