With an "insane" caliber I'd feel comfortable out to fifty yards.
Yes, a powerful enough handgun would have a range beyond 25 yards. My opinion was based on the markmanship skills of the typical shooter. IMHO, very few people would have the skills necessary to hit a vital area of a bear at 50 yards with a handgun. Let alone if the bear was charging you - moving, and you pumped up on adrenalin. An accomplished handgun hunter, with a scoped handgun, could certainly make the shot. But for the average Joe ... handgun group sizes at 50 yards are usually measured in feet, yards for some folks. But with a .444 Marlin handgun? Average Joes first shot might be within a few yards of the bear by pure dumb luck, but his followup shot would be more likely to take out the 747 flying overhead.