For me, the perfect Blaziken is this:
Nature Jolly
EVs: 4HP, 252 Attack, 252 Speed
Ability: Speed Boost
Item: Wide Lens
Moveset: Flare Blitz, Hi Jump Kick, Swords Dance, Protect
With it's dual stab, it can cover most of pokémons.
Having a 120 power fire attack with 100% accuracy anda
130 fighting power attack, with now 99% accuracy due to wide-lens,
your chance of hit is almost absolute, and combined with swords dance
you can one-hit ko almost every pokémon.
If facing a pokemon that can OHKO Blaziken, you can hide yourself with protect in the first turn
on second turn, you'll be faster than everything that has not a speed boosted or mega-evolved,
just avoid Mega-Aerodactyl, Mega-Alakazam and Deoxys.
If facing a pokémon that can't OHKO Blaziken you can Swords Dance once,
and with speed boost you not only be faster than it, but also will have a frightening 678 Attack,
combined with those two powerful fighting and fire attacks, you can OHKO almost everything,
and even sweep an entire team. If Mega-Alakazam or Mega-Aerodactyl were summoned after that,
they would be outspeeded by Blaziken and OHKOd by Flare-Blitz and Hi-Jump-Kick respectively.