No Counterplay?
Here is a list of items, abilites and sums that stop pykes execute from either hitting or resetting:
Flash
Heal
Sivir Spellsheild
Nocturne Spellsheild
Lulu R
Kayle R
Lucian Dash
Ezreal Blink
Kayn R
Sona W
Fizz W(? I've never played fizz)
Vlad pool
Camille R (timing is hard but doable)
Bard R (again hard timing)
Stopwatch
Zonyas
GA
Edge of Night (hard timing)
Katarina Jump
Zed Shadowstep (forgot what the ability is called exactly)
Trynd R
Fiora Reposte (did not used to work but was bugfixed)
Zilean R
Soraka W
Soraka R
Various Riven Dodges
Various Renekton Dodges
Shaco R
Taric R (hard timing)
malz Passive
Anivia Passive
Zac Passive
Mini Gnar Hops
Yasuo Dashes
Nami W
Leblanc Distortion
Lissandra self ult
Aatrox Ult
Khaazix hop
Lee Sin Q
Evelynn R
Sylas W
and probally a bunch more that I'm forgetting. But basically any dash/blink, any spellsheild (apart from morg black sheild), any invulnerability spell, Resurrection, or Heal stops pyke's execute from resetting at least and many stop it from doing anything at all.