1. Gamma Broodmother Lystrix

    You defeated the mother of all araneo on Gamma difficulty.

    Awarded 16 times

  2. Beta Broodmother Lystrix

    You defeated the mother of all araneo on Beta difficulty.

    Awarded 15 times

  3. Alpha Broodmother Lystrix

    You defeated the mother of all araneo on Alpha difficulty.

    Awarded 14 times

  4. Gamma Megapithecus

    You have defeated the Megapithecus on Gamma difficulty.

    Awarded 22 times

  5. Beta Megapithecus

    You have defeated the Megapithecus on Beta difficulty.

    Awarded 14 times

  6. Alpha Megapithecus

    You have defeated the Megapithecus on Alpha difficulty.

    Awarded 16 times

  7. Gamma Dragon

    You have slain the dragon on Gamma difficulty.

    Awarded 19 times

  8. Beta Dragon

    You have slain the dragon on Beta difficulty.

    Awarded 16 times

  9. Alpha Dragon

    You have slain the dragon on Alpha difficulty.

    Awarded 16 times

  10. Gamma Overseer

    You overcame the gauntlet of the Tek Cave in the islands volcano and defeated the Overseer in the starlit sanctuary on Gamma difficulty!

    Awarded 4 times

  11. Beta Overseer

    You overcame the gauntlet of the Tek Cave in the islands volcano and defeated the Overseer in the starlit sanctuary on Beta difficulty!

    Awarded 4 times

  12. Alpha Overseer

    You overcame the gauntlet of the Tek Cave in the islands volcano and defeated the Overseer in the starlit sanctuary on Alpha difficulty!

    Awarded 4 times

  13. Gamma Manticore

    You defeated the guardian of the desert on Gamma difficulty.

    Awarded 20 times

  14. Beta Manticore

    You defeated the guardian of the desert on Beta difficulty.

    Awarded 13 times

  15. Alpha Manticore

    You defeated the guardian of the desert on Alpha difficulty.

    Awarded 11 times

  16. Gamma Rockwell

    You defeated the former researcher "Sir Edmund Rockwell" in the depths of Aberration on Gamma difficulty.

    Awarded 12 times

  17. Beta Rockwell

    You defeated the former researcher "Sir Edmund Rockwell" in the depths of Aberration on Beta difficulty.

    Awarded 8 times

  18. Alpha Rockwell

    You defeated the former researcher "Sir Edmund Rockwell" in the depths of Aberration on Alpha difficulty.

    Awarded 5 times

  19. Desert Titan

    You defeated the Desert Titan of the desert proto ARK!

    Awarded 9 times

  20. Ice Titan

    You defeated the Ice Titan of the frozen proto ARK!

    Awarded 8 times

  21. Forest Titan

    You defeated the Forest Titan of the sunken forest!

    Awarded 4 times

  22. Gamma King Titan

    You defeated the King Titan in Gamma difficulty!

    Awarded 9 times

  23. Beta King Titan

    You defeated the King Titan on Beta difficulty!

    Awarded 9 times

  24. Alpha King Titan

    Amazing! By defeating the King Titan on Alpha difficulty, you activated the ARKs' reboot signal. The ARKs return to earth and cleanse it from all the element in the ground!

    Awarded 9 times

  25. Gamma Ascension Implant

    Received by defeating the Gamma Overseer. This implant increases your maximum level by 5.

    Awarded 4 times

  26. Beta Ascension Implant

    Received by defeating the Beta Overseer. This implant increases your maximum level by 10.

    Awarded 4 times

  27. Alpha Ascension Implant

    Received by defeating the Alpha Overseer. This implant increases your maximum level by 15.

    Awarded 4 times

  28. Gamma Aberrant Implant

    Received in the depths of Aberration by defeating Gamma Rockwell. This implant increases your maximum level by 5.

    Awarded 12 times

  29. Beta Aberrant Implant

    Received in the depths of Aberration by defeating Beta Rockwell. This implant increases your maximum level by 10.

    Awarded 8 times

  30. Alpha Aberrant Implant

    Received in the depths of Aberration by defeating Alpha Rockwell. This implant increases your maximum level by 15.

    Awarded 5 times

Image Sources: http://ark.gamepedia.com