Bad, boring, poor, or awful. Those are opposites for splendid.
For the word "splendid," the comparative is more splendid and the superlative is most splendid
"Splendid" doesn't have a comparative and superlative form. Instead, you would say "more splendid" or "most splendid."
more splendid, most splendid
more splendid, most splendid
The view from the mountaintop was absolutely splendid, with the sun setting over the horizon in a colorful display.
more splendid
The superlative degree of "splendid" is "most splendid."
Possessing or displaying splendor; shining; very bright; as, a splendid sun., Showy; magnificent; sumptuous; pompous; as, a splendid palace; a splendid procession or pageant., Illustrious; heroic; brilliant; celebrated; famous; as, a splendid victory or reputation.
She has such a splendid face
Splendid Animation was created in 2001.
Splendid Fellows was created in 1934.