I know that LiCo cells aren’t safe below 2-2.5 volts.But what about IMR’s? I ask because I just found an AW 16340 dead in a small light. Funny thing it was not on, but the cell is at zero volts.I placed in my Vc4 and it started charging as an NiMh cell then quickly switched to LiIon charging.I only did this for a few then stopped it to check in with some smarter people here! 
Once an IMR cell drops below 2.5V the safest bet is to recycle it.
Some folks have revived dead cells and shared it here, but it is a touchy operation requiring constant supervision and monitoring plus extended safety precautions. Even then many of the revived cells die soon afterward, but a few do come back to life. If the cell “goes boom” when charging you lose the charger too.
With cells being so cheap and plentiful now I just don’t think it’s worth the risk, YMMV.
Phil
i have woke a few up, using my smallest (smallest current) charger. A few went on nimh charging before getting them to take a charge.
I always MONITOR THEM when doing this, and feel for HEAT… only ONE of them got super hot, and i tossed that one… the others were okay and worked normally after that. But, i assume they dont have nearly the capacity they once had from being run so low…