[Boaz]

Regarding Syrio's encounter with Ser Meryn of the Kingsguard...

First, Ser Meryn survived. Syrio killed or wounded five Red Cloaks, but not Meryn.

Second, Syrio sent Arya away. If Syrio planned on killing Meryn and escorting Arya to safety, then he'd have killed Meryn. Meryn survived.

Mayhaps, Syrio ran away from Meryn. But remember, Syrion tut-tutted Arya and said something like, "The first sword of Braavos does not run."

So Syrio and Meryn faced off with weapons. Syrio would not run. Meryn survived. I think the conclusion is that Ser Meryn chopped Syrio into many pieces.