Hurtgen Forest - 50 Square miles, 30,000 casualties killed and wounded with some of the difficulty being inexperienced units who fell apart during their first severe combat. Approximately two months until secured.
Saipan - 44.6 Square Miles, 3,225 KIA, 13,061 WIA, approximately one month until secured.
Betio - 3.5 Square miles, 920 KIA, 2,200 WIA, secured after three days.
Iwo Jima - 8 Square miles, 6,000 KIA, 25,000 WIA, approximately one month until secured.
On a per square mile basis, Iwo was the clear worst place on earth in terms of dead and wounded. I'm not sure what is driving your stubborn insistence that "other battles were just as bad" but even though all of the battles you cited were hell on earth, Iwo was still the worst of them all. I encourage you to read more about it.