Level 20 fighters get your four attacks, multiple action surges, and save re-rolls, plus whatever subclass abilities you go with. Barbarians get those sweet sweet Str and Con boosts at Level 20. If you grab the Tough feat along the way, I believe that's 325 HP using the fixed values instead of rolling, if you maxed your Str and Con to 20 before getting that capstone ability. Who wouldn't love that?
Multiclassing a full caster would mean giving up 9th-level spells since you get them at 17, but I'd probably enjoy a Blade Warlock 12/Fighter 8. Warlocks with Bard dips can be fun too, you can use the lower level Bard spell slots for spells that don't scale, like Hex(ok yes technically it does scale, but do you really want to keep concentration going for 24 hours?), Misty Step etc. And save your 3 Pact slots for stuff that does scale, potentially a nice 5th-level heal in an emergency.
In my first 5e campaign I played a Fighter(Battle Master)/Rogue(Assassin) archer up to 13th level(Fighter 8/Rogue 5) that was a lot of fun. Scaling that up to 20th level, I would probably do 12/8 one way or the other, but most likely Fighter 12 since I like their 9-12 abilities better(especially that 3rd attack at F11).
ncG1vNJzZmivp6x7prrWqKmlnF6kv6h706GpnpmUqHypscupZKWunGJ%2FcXnOp5xmq5ikwW6y1Kdkm62ZobG0epRxb3FxYWQ%3D