so as we all know deathstroke turned evil because of the mixed effects caused by mirakuru and oliver choosing to save sara, not shado when fyer gave him a choice.
and as it looks like shado didnt die. in the latest arrow episode, oliver met shado when he was in hong kong.
They cured roy from mirakuru. so that part is curable. and since shado is alive. the remaining part of the problem can be cured.
just cure that romantic super villian!!!