Amore serves as the go-to term of endearment that numerous Italian men and women opt for when addressing their significant other. It's the nickname I use for my husband, even in moments of anger!
Caro (fem: cara) is one of those expressions that can be employed with almost anyone you hold dear. However, when used to address your partner, it may come across as slightly formal.
One adorable Italian nickname that I consistently use is cucciolo (feminine: cucciola). I find it preferable to many other choices since it exudes a playful and endearing quality.
Italian men who possess a strong romantic inclination may desire to bestow their significant other with the "royal treatment" by referring to her as principessa, meaning princess.