I think the above "avvincente" doesn't convey the exact meaning of "addicting" at all. In fact, "avvincente" means something that is exciting, absorbing or really interesting: "una storia avvincente".
"Assuefacente" sounds too complicated a word (even for Italian standards) for every-day speech.
I have two different translations for "addicting":
"Social media is so addictive; I could stay on Facebook for days" = "I social network sono una droga; potrei stare su Facebook per giorni". This is a very informal expression, that you can use with friends or family. It perfectly reflects the English meaning of "something addictive like a drug."
"A lot of people find yoga addictive after a month or so" = "In molte persone lo yoga crea dipendenza dopo un mese circa". This expression can be used in a formal context, but won't sound unnatural even if you use it with friends: it will just show that you have proper knowledge of the language!
"Crea" is the verb "creare": io creo, tu crei, egli crea, noi creiamo, voi create, essi creano.
As for the expression "I'm addicted to....":
-"I'm addicted to you" = "Mi crei dipendenza" / "Sei la mia droga" (Watch out: don't say "Sono dipendente da te"/"dipendo da te" has a slightly different meaning: it means "I depend on you").
-"I'm addicted to yoga" can be translated with "Lo yoga è la mia droga", "Sono drogato di yoga" (both informal), "Non posso fare a meno dello yoga", "non posso vivere senza lo yoga".