Most of the ones that get close or have more are:
DOT abillities, such as Fiddle W and R (225% AP over 5 sec + base), Wukong R (440% AD over 4 sec)
Multi-shot: Lucian R (500-750% AD + 200-300% AP over 20-30 shots), MF R (900-1200% AD over 12-16 shots), Heimer RW (183% AP over 4 waves of rockets + base), Xerath R (215% AP at max rank if you hit all 5 shots + base)
The only single damage instance ults that come close are Lee Sin R (200% bonus AD + base), Nunu R (250% AP after 3 sec channel + base), Veigar (up to 150% AP on targets below 33% health + base), Cait R (200% bonus AD + base)
So yeah, there are some ultis that can do more damage, but they have some sort of condition, such as a channel or DOT or having to hit multiple shots.