Seriously, I know that Percy's the MC (in fact all the 4KoA are MC but Percy's a little bit more) but I don't see any reason for him to be stronger than others, especially Tristan. This one is the son of the previous MC, and most importantly,
he shares almost the same substance as Chaos itself! Chaos was defined as an entity made of "Impure Darkness & Pure Light":
Meliodas described it as "a power that's both a
Blessing & a
Curse", Tristan was stated in the prophecy to
possess both Holiness (Blessing) & Evilness (Curse) in the eyes:
Arthur's Excalibur contains both
wings of Demons & Angels and whenever he uses the power to create or manipulate reality a pattern made of
white &
black squares appears on the ground:
In a nutshell, I believe that Tristan is the most special among the 4KoA because he is the "
closest being to Chaos"