Supeudol
Bluelighter
not sure I agree with that one, its a bit of a sweeping statement and would require you to fully define addictive, how hard a substance is to withdraw from also doesn't really have scale and would clearly depend on both the initial habit, the individual and a whole heap of other variables.
I agree people often don't take the addiction and withdrawal potential seriously enough but to put them at the very top of the scale doesn't sit right with me although I'd be interested as to how you would substantiate that position.
Once you have done a ton of opiates and benzo's for years on end, (Extremely heavy doses of both). You will see which is worse, obviously benzodiazepines are the harder drug to withdraw from, because the physical withdrawals can last months to years.
There is no other drug where the physical withdrawals can last months to years like benzodiazepines.
Google 'Benzodiazepine Withdrawal' and take a look at the Ashton Manual.
Opioids are a cake walk to come off compared to Benzo's. And I have used a ton of opioids for years including fentanyl, very high doses of hydromorphone, oxycodone, and morphine.