Unsafe = Well that depends entirely on the move you want to punish. I usually punish with 4T and 6T. Note that both of these throws are equally quick. Use 6T if you opponent is with his back to a dangerzone or a wall, and use 4T if you are with your back to a dangerzone or wall. So whether you'll use 4T or 6T depends entirely on environmental positioning.
You can punish with 66T and 41236T too but that is difficult imo due to the many directions you have to input. Use those throws as strong punishes against very unsafe attacks (66T for -11 or worse and 41236T for -13 or worse).