(18:74) So they set out, until when they met a boy, al-Khidh r killed him. [Moses] said, “Have you killed a pure soul for other than [having killed] a soul? You have certainly done a deplorable thing.”
Muhammad Taqi-ud-Din al-Hilali and Muhammad Muhsin Khan,
(18:74) Then they both proceeded, till they met a boy, he (Khidr) killed him. Musa (Moses) said: “Have you killed an innocent person who had killed none? Verily, you have committed a thing “Nukra” (a great Munkar – prohibited, evil, dreadful thing)!”
Mohammed Marmaduke William Pickthall
(18:74) So they twain journeyed on till, when they met a lad, he slew him. (Moses) said: What! Hast thou slain an innocent soul who hath slain no man? Verily thou hast done a horrid thing.
Abdullah Yusuf Ali
(18:74) Then they proceeded: until, when they met a young man, he slew him. Moses said: “Hast thou slain an innocent person who had slain none? Truly a foul (unheard of) thing hast thou done!”
Mohammad Habib Shakir
(18:74) So they went on until, when they met a boy, he slew him. (Musa) said: Have you slain an innocent person otherwise than for manslaughter? Certainly you have done an evil thing.
Dr. Ghali
(18:74) So they (both) went off until, when they (both) met a youth, then he killed him. He said, “Have you killed a most cleansed self without (his having killed another) self? Indeed you have already come with a (highly) maleficent thing.”
Ali Unal
(18:74) So they went on until, when they met a young boy, he (al-Khadr) killed him. (Moses) said: “Have you killed an innocent soul (not in lawful retaliation but) without his having killed anyone? Assuredly you have done a horrible thing!”
Amatul Rahman Omar
(18:74) Then they both set out again till when they met a boy, he (- the great man) slew him. (At this Moses) said, `Why have you slain an innocent person without (his having slain) any one. Most certainly, it is a strangely wondrous act you have committed.´
Literal
(18:74) So they (B) left/set out until when they (B) met/found a servant/boy , so he killed him. He (Moses) said: “Did you kill a pure self without a self? You had come (with) an awful/obscene thing.”
Ahmed Ali
(18:74) The two went on till they came to a boy, whom he killed. Moses exclaimed: “You have killed an innocent soul who had taken no life. You have done a most abominable thing!”
A. J. Arberry
(18:74) So they departed; until, when they met a lad, he slew him. He said, ‘What, hast thou slain a soul innocent, and that not to retaliate for a soul slain? Thou hast indeed done a horrible thing.’
Abdul Majid Daryabadi
(18:74) Then the twain journeyed until when they met a boy, and he killed him. Musa said: hast thou slain a person innocent not in return for a Person Assuredly thou hast committed a thing formidable.
Maulana Mohammad Ali
(18:74)-
Muhammad Sarwar
(18:74) They continued on their journey until they met a young boy whom he killed. Moses said, “How could you murder an innocent soul? This is certainly a horrible act”.
Hamid Abdul Aziz
(18:74) Moses said (pleaded), “Rebuke me not for forgetting, and be not hard on me.”
Faridul Haque
(18:74) So they set out again
Talal Itani
(18:74) Then they set out. Until, when they encountered a boy, he killed him. He said, Did you kill a pure soul, who killed no one? You have done something terrible.
Ahmed Raza Khan
(18:74) So they set out again; until when they met a boy, the chosen bondman slew him Moosa said, Did you slay an innocent soul not in retribution for another? You have indeed done an extremely evil thing.
Wahiduddin Khan
(18:74) So they travelled on. Then they met a young boy and the man killed him. Moses said, “Have you slain an innocent person without his having slain anyone? Indeed, you have done a terrible thing!”
Safi-ur-Rahman al-Mubarakpuri
(18:74) Then they both proceeded till they met a boy, and he (Khidr) killed him. Musa said: “Have you killed an innocent person without Nafs Verily, you have committed a thing Nukr!”
Ali Quli Qarai
(18:74) So they went on until they came upon a boy, whereat he slew him. He said, Did you slay an innocent soul, without [his having slain] anyone? You have certainly done a dire thing!
Hasan al-Fatih Qaribullah and Ahmad Darwish
(18:74) and so they departed. Thereafter they met a boy and he killed him. He (Moses) exclaimed: ‘What, have you killed a pure soul and it was not done (in retaliation) for a soul you have done a terrible thing’
That is translated surah Al kahf ayat 74 (QS 18: 74) in arabic and english text, may be useful.