This is my guide on how to get the Corrupted Sword the easiest way (I got it first attempt, or got really lucky).

SHOP:
-Toggling ON the important items, and toggling OFF the unimportant ones.
-Keeping the WEAPON and TOME as 2 slots ONLY (Recommended)

SET-UP:
-I used Tony McZoom since he's one of the fastest character to roam around the map.
-Map: Dessert TIER 1 (Challenges)
-HYPER

IN-GAME:
-Prioritizing SHRINES and CHESTS.
-Movement Speed and Damage BUFFS/ITEMS.
-Time priority until finding portal and beating the boss would be 2:00 MINUTES LEFT.
-Shortest time of killing the boss would be 10-20 seconds.

LATE GAME: (After killing the boss)
-Time limit for earning XP after killing the boss would be 1:30 MINUTES (YOU MUST SURVIVE AT ALL COST).
-Leaving ONE Magnet Shrine would guarantee you of earning as much XP as possible.

(GUIDE UPDATED)