Excessive means beyond what is typical or normal. When something is excessive, there's way too much.
Excessive refers to something that is extra — usually in a negative way. A 90-second drum solo in a two-minute song is excessive. Getting down on your knees and kissing someone's feet to thank them for a favor is excessive, unless they gave you their firstborn. Often this means something that exceeds the bounds of good taste, or is extravagant and inappropriately expensive. You should dress up for dinner, but wearing a ball gown to a diner is excessive.