Amazing & awful
Strong reactions at both ends of the scale: amazing, best, worst, terrible, and yabai, which can mean either.
sugoi
polite sugoi desuamazing, incredible
すごい すごいです
The all-purpose impressed reaction ('sugoi!') to people, skills, views and news; it also marks sheer intensity, good or bad (sugoi ame = torrential rain), and as sugoku it becomes 'really, very' (Degree, amount & limits).
kono uta, sugoi ne
This song is amazing.
この歌、すごいね
kono uta, sugoi desu ne
This song is amazing.
この歌、すごいですね
The rough male sugee is heard all the time in dramas; recognise it, but say sugoi. Casually, bare sugoi also works as 'really' (sugoi oishii = really tasty); with desu, use sugoku or totemo.
Learn alongside: yabai
saikou
polite saikou desuthe best, awesome
最高 さいこう 最高です
The top-end enthusiastic verdict on a day, meal, person or experience ('saikou!'); it takes da or datta like a noun.
kyou, saikou datta
Today was the best.
今日、最高だった
kyou wa saikou deshita
Today was the best.
今日は最高でした
Learn alongside: saiaku
saiaku
polite saiaku desuthe worst, awful
最悪 さいあく 最悪です
The top-end complaint about a day, event, person or situation; said alone, 'saiaku!' is the standard 'ugh, terrible' reaction to bad luck.
kyou, saiaku datta
Today was the worst.
今日、最悪だった
kyou wa saiaku deshita
Today was the worst.
今日は最悪でした
sai-kou and sai-aku only differ after sai-, so hear the whole word before you react.
hidoi
polite hidoi desuterrible, cruel, harsh
ひどい ひどいです
Says something is terrible (weather, a cold, traffic) or that someone is mean or unfair; 'hidoi!' is the reaction to being treated badly, and 'sore wa hidoi' is sympathy for someone's story.
sore wa hidoi ne
That's awful.
それはひどいね
sore wa hidoi desu ne
That's awful.
それはひどいですね
Said to someone's face, 'hidoi!' means 'that's mean!'
yabai
polite sugoi desu / mazui desucrazy (good or bad), uh-oh
やばい すごいです / まずいです
Casual intensity word with two senses, 'uh-oh, I'm in trouble' (the original) and 'insanely good' (younger speakers); tone and context decide which.
kono uta, yabai ne
This song is insane.
この歌、やばいね
kono uta, sugoi desu ne
This song is amazing.
この歌、すごいですね
The 'uh-oh' sense: 'yabai, okureru!' = Oh no, I'm going to be late! Don't use it with clerks or strangers: politely, say sugoi desu for the good sense and mazui desu for the uh-oh sense (mazui desu ne, okuremasu).