Venom overdose
Venom was a top secret super steroid, developed in Project Gilgamesh, that granted super-strength and increased physical durability to its user. However it had addictive effects and the user must use it periodically or suffer long periods of physical weakness. Likewise, a constant infusion is needed to sustain the effect for long periods of time, if the supply of Venom is halted, the user immediately returns to normal. Excess injection of Venom at once will cause pain to the user and risk death. Long term usage will cause significant body degradation until the user's system fatally collapses. At that point, the only thing capable of sustaining the users body is Venom itself. The potency of Venom is such that even decades after development there is still no drug capable of rivaling Venom in power.
Bane was the best known user of Venom to increase his speed, strength, stamina, endurance and also his size. With help of the drug, Bane became an international assassin for hire.