Tsuna at current ( Tsuna with original ring and Yusuke at battle with sensui )
Win by death
Cell Games Arena
How does one react to light speed and be unable to move at light speed? Your mind must first comprehend beyond that speed then accelerate your muscles to that speed as well. Yusuke cannot even put up a good fight if Tsuna is in that dying will state. But Yusuke will probably win if they are in character with no motivation to fight because at base tsuna is unwilling to fight and will talk as yusuke will punch him in the face and knock him out. Now if they know its a death match from the start then I will say Tsuna wins.
Tsuna has never proven to be light speed. He merely reacted to it.
You cannot react faster than you can think fact. Like TNO already said, your mind must first comprehend beyond that point and then your muscles must be able to move at that speed. Yusuke wins in character Tsuna stomps in a death match.
There is seemingly no 'perfect' way to truly say goodbye. So I gathered a bunch of them!