Excessive amounts of light can fry particularly vulnerable subregions of the bacterium-sized working region. This is probably how most instant damage occurs. Please note that laser diodes make laser light more easily and more efficiently at lower temperatures, and it is sometimes possible for a laser diode to be ruined by a given current at low temperatures that it survives at warmer temperatures. Most diode laser modules have feedback systems based on the photodiode included in the laser diode to stabilize beam output. Laser diodes are easily ruined by static electricity.
Static electricity can briefly exceed maximum safe forward currents even if barely noticed.
If static voltage should be applied in reverse polarity, things are even worse. Yes, some laser diodes have survived worse than looking at them the wrong way. You may get lucky and be able to just throw something together and have it work. Good luck, try only at your own risk to get a laser diode to work. Meanwhile, you might want to consider some messy limitations about minimum theoretical divergence of laser beams.