The word(s) "extremely" appears 4 time(s) in 4 verse(s) in Quran in Mohsin Khan translation.

(1) And seek help in patience and As-Salat (the prayer) and truly it is extremely heavy and hard except for Al-Khashi'un [i.e. the true believers in Allah - those who obey Allah with full submission, fear much from His Punishment, and believe in His Promise (Paradise) and in His Warnings (Hell)].

(2) The likeness of what they spend in this world is the likeness of a wind which is extremely cold; it struck the harvest of a people who did wrong against themselves and destroyed it, (i.e. the good deed of a person is only accepted if he is a monotheist and believes in all the Prophets of Allah, including the Christ عليه السلام and Muhammad صلى الله عليه وسلم). Allah wronged them not, but they wronged themselves.

(3) And We decreed for the Children of Israel in the Scripture: indeed you would do mischief in the land twice and you will become tyrants and extremely arrogant!

(4) That was because you had been exulting in the earth without any right (by worshipping others instead of Allah and by committing crimes), and that you used to rejoice extremely (in your error).