What withdrawal symptoms are more extreme - in heroin, crack cocaine or alcohol, in order?

Too subjective to do: People's reports of 'withdrawal' vs. Objective measurements (vital signs) - what a mess. Heroin withdrawal is very painful/achy and people hate it- but it doesn't 'kill'. Yet a sudden withdrawal from alcohol could cause memory loss and seizures - far worse in my opinion. Depending on what you call extreme, i would say alcohol !