Badly.
I miss you terribly, would be better.
No, it should be "She sings badly."
No. The sentence should read "She sings badly."
badly, horribly, unbelievably, extremely, seriously
very, extremely, terribly, exceptionally, greatly, immensely, exceedingly, badly, woefully
No, it's an adjective. The adverb form is terribly.
That is the correct spelling of the adverb "badly" (poorly, or fervently).
my brother behaved badly with me
There are many better ways to say this, such as "You're not a (very) good painter" "You don't paint well" "You're a bad painter" "You painting lacks (what it lacks)" "You paint horribly" But "You paint badly" works.
badly hope i helped!
The classroom was reeking badly.
badly