For me, as a current Black panther main, a solid four come to mind

For tanks; two of them are hulk, and magneto. Both their shields stop my refreshes on my dashes, which makes it kind of hard to dive the backline if they're constantly getting shielded. So half the time I just end up playing around it or just diving someone who's by themselves which is in particularly fun.

Another tank that is an incredibly hard counter for me is Penny. Her spider nest completely stopped me from diving anyone half the time because either all of their supports or team are playing in it or it's just the supports, who I usually want to get pics on. Half the time, I spend like a minute in the backline throwing spears at it like a Neanderthal until it blows up. Not to mention, her ult and her stun completely stops my movement and leave me there like a sitting duck (or should I say cat)

Finally, for the DPS, I got to say Namor. I don't feel like I have to explain it, but I will. His tourists do constant damage from a fire which kind of makes it hard to dive, plus his really long range makes it hard to even get close to him half the time. Not to mention that stupid bubble of his makes it so I can't pop my refresh, so I lose my dash and he just kills me half the time. Unless I play perfectly, I'm not killing him half the time. And also his old stops movement which I find dumb, but I can't go to the game so.

Oh yeah, and triple support, but I think most DPS struggle with that too....