There are a lot of ways to counter both ults. Ivy stomp counters both. But any stun really so knockdown, lightning scroll, etc.

Against dynamo ult there is paige ult, infernus ult, lash ult, unstoppable, rescue beam to pull others out of it, ivy ult also pulls others out.

The best way to deal with both is however sinclair imo. A good sinclair makes me as a dynamo player scared to be at teamfights because i dont wanna get my team ulted by him.

They are strong ults but I feel like there’s a fair amount of counter play. Besides knockdown there’s items like curse, rescue beam, unstoppable, indomitable.

Like the other comment mentioned, a lot of characters ults or skills can interrupt if timed right. Saving Paige ult to interrupt a black hole and heal your team is extremely satisfying.

If you know their ult is up, do your best to position strategically outside the range. Against Seven, know where the closest cover or veil is and be ready to pivot and change course if you think he’ll use it.