Kassandra running faster than explosions
In the Palace of the Kolossi, she has to run faster before the explosion catches up with her. It's a mandatory cinematic, so it's part of Kassandra's lore.
Kassandra started with a 7m advantage ahead of the explosion and was never caught, so at a minimum she would have to maintain a running speed of 1,235 km/h (27.6 times faster than Peak Human). That's the bare minimum, since the ISU device far exceeds that power.
Besides speed, Kassandra obviously has great durability since she was never injured (lungs, ears, etc), and the explosion never unbalanced her (her feet never slip, and her legs never lose their stride either).
Naturally, Ubisoft or any other company will show their characters running at those speeds without making it cinematic, since basically no one would be able to see anything while playing. That's why in gameplay she runs at around 24 km/h, to balance the game (like Bayonetta, Cloud Strife, Dante Sparda, and other absurdly fast but gameplay-limited characters).