Yeah, kratom is a full-blown partial opioid (make out of that sentence what you want).
Opioids unfortunately don't need to be full agonists to be habit forming (see bupe - tramadol is a bad example because it metabolizes to a full agonist but Kratom has that too in 7-HO-mitragynine which, like the HO-arylcycolohexylamines, is a full agonist). In animals mitragynine wasn't dependency forming but 7-HO was. Now the tricky point, your body metabolizes each of these into the other compound, so it's kinda pointless. Kratom is a full opioid, just herewith I forbid you to use this information in any anti-drug context, Kratom is good to be legal and should stay legal, just with a warning.
I am currently recovering from morphine maintenance and while morphine is way less bad than methadone, so is probably kratom than morphine, they all are no joke but methadone is a horrible beast while morphine is made by your own body (I can post the link again if somebody's interested) and all things which are made by ourselves (not in a lab, that is) tend to be less bad than completely exogenous things like e.g. fentanylderivates. Or methadone. From what I get from up to 600mg/d morphine I was surprised that it wasn't more but also surprised in a bad way because while anxiety would be the absolute worst, this depressive misery is what comes next to that. No anxiety though, for what I am grateful. There would be drugs which make you skip withdrawal, probably, as probably as I expected anxiety to be a major problem of opioid withdrawal. It's not tested so far as I only got heavily addicted when I stopped having arylcyclohexylamines around (again, make out of that what you want).