Forward biasing a diode past built-in voltage
As you increase the voltage across the forward-biased diode, the current increases exponentially, as does power dissipation in the diode. Eventually this exceeds the thermal capacity of the diode. This kills the diode.

$$I = I_s\Big(e^{\frac{V_D}{nV_T}}-1\Big)$$

where

I is the diode current,
IS is the reverse bias saturation current (or scale current),
VD is the voltage across the diode,
VT is the thermal voltage, and
n is the ideality factor