Senna vs Miss Fortune

Attack the souls held by the Mist whenever you can: each soul freed with Absolution (passive) increases your AD, attack range and crit chance.

Fire Piercing Darkness (Q) through an ally or an enemy to hit both: the beam heals your allies, and damages and slows enemies in the line.

Cast Last Embrace (W) on a target that's already slowed or immobilized: after a short delay, they and nearby enemies are rooted.

Cast Curse of the Black Mist (E) to engage or escape with your team: allies who enter it are camouflaged, then fast and unselectable.

Cast Dawning Shadow (R) to save an ally across the map: the beam has unlimited range and shields allies.

Don't stay behind a low-health minion: if Double Up (Q) kills it, the bounce that hits you always crits.

Hit her regularly, even with a small hit: Strut (W) only grants her passive move speed after a few seconds without taking damage.

If you can engage, get on top of her: Miss Fortune has no dash or leap, only the speed from Strut (W).

If you have CC, save it for Bullet Time (R): she channels in place, and interrupting her cancels the remaining waves.