1.The dog smells badly.
2. I only ate three slices of pizza.
3. You sure can eat a lot of ice cream at one sitting !
1) This might be correct- depends on what you mean.
If the dog stinks ; The dog smells( linking verb) bad . ( Adjective)
If the dog has a poor sense of smell ; The dog smells (action verb) badly.
Ans 2) I ate only three slices of pizza.
Ans 3) You surely can eat a lot of ice cream at one sitting! ( sure is an Adjective, however here Adverb is required ).