Older aircraft, H-19 (Whirlwind in British vernacular), H-34 (Wessex in British vernacular), Chinook CH-47A, most any helicopter in reality can be pushed hard and encounter Retreating Blade Stall.
My basic rotary training course was in the RAF Whirlwind 10 (single turbine, floppy stick, quite a big aircraft for a basic trainer). As part of the course we were sent up to 10,000 feet so the QHI could demonstrate RBS. My instructor did his thing, which was a less than convincing demo because not much happened apart from a bit of vibration, then said:
"There, that was RBS, did you see it?"
"No..." said I, being honest.
"Well I'm not doing it again!" came the reply, and he didn't!
But my previous QHI (sadly killed in a motorcycling accident during the time of my course) had already inadvertently given me a far more effective demo. One morning he took control as I approached our relief landing ground. He lowered the nose and descended rapidly (for a Whirlwind) to about 150 feet, then pulled the aircraft into a very steep turn. The old Whirly didn't like that and all by itself it rapidly rolled about 90 degrees left and pitched hard up! Now THAT was RBS!
Thankfully, he had turned right, so the aircraft rolled upright. Had it been a left turn, I probably wouldn't be here because the aircraft would have rolled inverted.
He apologised to me later, debriefed me on what had happened and I think we both learned a lesson about flying from that.