I'm talking about characters planet/star-system/galaxy-sized. Characters like Unicron, the 2001: A Space Odyssey baby, and even meta-characters, like Tenga Toppa Gurren Lagann (a ship powered by all of humanity's fighting spirit) would count in this list. The Borg Collective is also something I would consider, as each individual unit considers themselves the same as the whole. I would only count characters who can change size at will if they ever were depicted as growing to such a size, or if there is a related, official story/myth of them ever doing this.
I've done many searches, and can't find a list with characters on this scale. The best list I found was one that featured a 30-foot human somewhere near the middle.