Originally Posted by Morello
It will nullify the CC and reflect damage. It won't reflect the CC.
quick correction: fiora's riposte does not
riposte will 'block' all of the damage from the next valid attack, but effects like red buff, the slow from frozen mallet, and the knock-up from blitz's powerfist will all still go through.
in regards to multi-hit attacks (like renekton's ruthless predator), it should block the damage from the first hit only (iirc), and she would be susceptible to any/all effects applied by any of the hits.
it works a lot like pantheon's passive, for those of you familiar with him.