In hindsight, he said he wished he had not exposed Pioneer employees to Exxon’s “notoriously cut-throat and dysfunctional culture” but instead pursued takeovers of other US oil companies such as Range Resources or Endeavour Energy Resources.
https://finance.yahoo.com/energy/articles/shale-tycoon-claims-exxon-ceo-124336695.html
https://www.ft.com/content/ad6d56fa-6a6e-43bd-8f12-205a3f94ac0e?syn-25a6b1a6=1