The boy is chased by bees and he runs panickedly
Is there a better phrase or idiom that more can replace runs panickedly to make the sentence more vivid?
The problems with panickedly are that a) it's a made-up word b) it doesn't sound very elegant c) it's an adverb, so it describes the way that the boy runs. What you most likely want to do is to describe the state of the boy as he runs. The neatest way to say this would be to use a participle phrase (of just one word):
The boy is chased by bees and he runs, panicked.
Here, panicked describes the state of the boy, not the way that he runs.