Maximum Transistor current and voltage
Many power transistors have a SOA (Safe Operating Area) graph in their datasheet, here's an example:



The safe area is the bottom left side so:

Vce = 5 V at Ic = 20 Amps is just OK

but

Vce = 50 V at Ic = 2 Amps is not

Also note that it states Tc = 25 degrees Celcius meaning you have to cool this device such that its case will not exceed 25 degrees Celcius.

Also not that for a limited time, the device can handle a little higher value. It is not clear how much time it needs to recover after such an event.