i-adjective
Used for negative extremes: something frightening, severe, or shockingly bad. Often in the pattern すごい〜.
すごい嵐で電車が止まった。
A terrible storm stopped the trains.
彼の部屋はすごい散らかりようだ。
His room is dreadfully messy.
i-adjective
amazing; great; wonderful; terrific
Used for positive extremes: impressive, excellent, or surprisingly good. Very common in casual speech.
このラーメン、すごいおいしい！
This ramen is amazingly delicious!
彼女の英語はすごい上手だ。
Her English is really great.
i-adjective
vast; enormous; tremendous (in scale or number)
Emphasizes a large quantity, scale, or degree. Often used with numbers or amounts.
すごい数の人が集まった。
A tremendous number of people gathered.
この仕事にはすごい時間がかかった。
This work took an enormous amount of time.
adverb
Colloquial adverbial use, often as すごく or すごい directly modifying adjectives/verbs. The すごい+adjective form is common in casual speech but considered less formal than すごく.
See also: 凄く
今日はすごく暑いね。
It's awfully hot today, isn't it?
すごい疲れたから、もう寝る。
I'm really tired, so I'm going to bed.