Some notable players that didn't make it to the PGR top 50 (or in the case for Fatality, low placed in the PGR) includes Elegant, Sonido, Fatality, and Maister (this comment may age poorly, because there is an outside chance that Maister has sneakily made it).
These four has amassed some impressive results right now, with them growing ever so more, but all four of their PGR placements are held down heavily by their rather lackluster showings early in the season.
all play noticeably differently than their SSB4 counterparts, and it took time for these four players to adjust to their changes. It is paying off today, but since the PGR impacts their earlier performances, it affects their overall rankings for the entire season for the worst. If their performances today continues, these four could end up deep within the season 2 PGR rankings.
Two things to note:
1. LeoN
placed very well in the PGR at 35th. However, the cool thing about this is that season 1 doesn't count his performance at Defend the North 2019, as that is a season 2 tournament. Things are looking well for LeoN's season 2 PGRU appearance, especially if he keeps up the good work.
2.
sort of fall to the same category as the four characters listed above. However, SDX and Konga have both been inactive for a long time. Konga hasn't competed ever since Genesis 6, and despite SDX stringing impressive performances early on to the game (which is notably before Mewtwo's 3.0.0 buffs) which landed him the A51 spot, SDX decided to retire (sometimes poking his nose out in a few locals, but even that is rare).
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This here is completely my opinion, and some of you may disagree with me, but I don't really think the earlier events in Ultimate's lifespan should hold much weight to the overall rankings of season 1. Genesis 6 is one of the earliest events, yet holds one of the most value in the rankings. During that time period, the metagame was really young and players/characters were in a pretty underdeveloped state.