We don't have any and never did.
In 1961, the Soviets came within a factor of two, with a 58-megaton bomb. It was supposed to yield 100 megatons, but they decided to replace the U-238 tamper with lead, in the interest of reducing fallout, which was already becoming a world opinion issue. In the event, 97% of its yield was from fusion, and it produced very light fallout, having exploded at an altitude of 13,000 feet.
I added an extra zero just for effect.