“No offense, but ... ”

Not only is this a condescending phrase that signals a lack of respect, it is also a common passive-aggressive one.

Instead of passively saying you don’t want to offend and then doing it anyway, you could directly state, “I’m concerned what I say might upset you, so I want to know: Do I have permission to give you feedback on something?” or “I’d love for us to build trust so we can have really open dialogue with each other. What do you think?”