more badly, most badly
worse, worst
yes badly is an adverb because badly describes how we perform.
more badly
Badly
more badly
The prefix for "led badly" is "mis-", so it would be "misled badly."
The adverb "well" is the usual opposite of the adverb "badly." If "badly" is used to mean "extremely or greatly" the opposite could be "slightly." E.g. He was badly bruised./He was slightly bruised.
"Badly" is an adverb, not a noun. Can't be a possessive noun, unless your name is Mr. Badly, in which case it's "Mr. Badly's car".
Badly very badly
badly - schlecht.
Badly is an adverb.