Correcting a friend works best when they already know you’d take a hit for them.

Correction lands according to the relationship underneath it. The same sentence is either an attack or a kindness depending on whether the person already knows you are for them, and that knowledge is not built in the conversation itself, it is built in the months before. Without it, even accurate criticism just sounds like a verdict.

Spend the investment before you need it: show up, defend them when they are absent, be useful without being asked. Then when you do say the hard thing, say it privately, once, and stay close afterward. Presence after the correction is what proves the point.