I am here to remind all that Oberyn Martell, whilst being a sexy mo fo and loving paramour, also was smart as hell, forging SIX maester chains before he got FUCKING BORED and went on to form his own mercenary company.
During this time he fathered a half dozen bastards, but instead of abandoning them, he took responsibility and raised them to defend themselves and allowed them all an independence most fathers in Westeros would never allow their children, let alone daughters.
He was incredibly close to his sister and after her death attempted to raise the entire country of Dorne up around Viserys to overthrow Robert. Unable to do this, he never gave up the hope he’d one day avenge the atrocities committed against his sister and her children.
In short, too much heart was always Oberyn’s problem.