select a.hacker_id, h.name, a.cnt
from (
SELECT hacker_id,
             COUNT (hacker_id)                                                  cnt,
             MAX (COUNT (hacker_id)) OVER ()                                    mx,
             COUNT (COUNT (hacker_id)) OVER (PARTITION BY COUNT (hacker_id))    rep_cnt
        FROM challenges
    GROUP BY hacker_id
    ) a join hackers h on (a.hacker_id = h.hacker_id)
where not (rep_cnt>1 and cnt<mx)
order by 3 desc, 1 asc
;

WITH list_name AS(
    SELECT c.hacker_id, h.name, COUNT(c.challenge_id) AS challenges_created
    FROM Hackers h
    JOIN Challenges c ON h.hacker_id = c.hacker_id
    GROUP BY c.hacker_id, h.name
    ORDER BY COUNT(c.challenge_id) DESC, c.hacker_id),
    count_challenges AS(
    SELECT challenges_created, COUNT(challenges_created) AS counter
    FROM list_name
    GROUP BY challenges_created
    HAVING COUNT(challenges_created) = 1)
SELECT
    list_name.hacker_id,
    list_name.name,
    list_name.challenges_created
FROM list_name
WHERE list_name.challenges_created = (SELECT MAX(challenges_created) FROM list_name)
    OR list_name.challenges_created IN (SELECT count_challenges.challenges_created FROM count_challenges);