In LOCH, it is said that:
欧阳锋原想以蛤蟆功在郭靖小腹上偷按一掌,叫他三年后伤发而死
Ouyang Feng wanted to secretly hit Guo Jing on the stomach, so that the hit would take effect 3 years later and cause Guo Jing to die.
Does that mean the hit is so secretive that Guo Jing may not even know he was hit, and for the next 2.99 years, there would be little to no symptom until the 3 year time interval? If so, that is quite genius, and instantly puts Chen Jinnan's famed 7-day blood coagulation and Xie Xun's 7 Maim Fist detonation to minuscule worthiness.