Bisacodyl
"WORST PAIN EVER! I took one pill at 530pm. At midnight I nearly fainted from the horrific abdominal pains and cramps I was having. I poured sweat and felt like I was going too die. I have delivered two of my children naturally and I can tolerate pain, this however was  torture. I didn't even have a BM until the next day at 3pm. The cramping and nausea lingered for two more days after taking. I will NEVER take this medication again nor  recommend that anyone else take it."