Marvel Rivals is a free-to-play Marvel-themed PvP hero shooter. Compete against others and climb the ranks to prove your skill. This guide explains the Competitive rank reset system.
At the end of each Marvel Rivals Season, your Competitive rank decreases by seven tiers. For example, a Diamond I player will reset to Gold II. Players ending the season in Bronze III will remain at Bronze III.
The rank reset occurs at the Season's end. Season 1, starting January 10th (at the time of writing), will be the first reset.

Competitive mode unlocks at player level 10. You earn points to advance through tiers; 100 points per tier.
The ranks are:
Even after Grandmaster I, you can continue earning points for Eternity and One Above All. One Above All requires a top 500 leaderboard placement.
While Season 0 was short, future Seasons are expected to last approximately three months. New Seasons will introduce new heroes (like the Fantastic Four) and maps, giving you ample time to climb the ranks.