S/A+/Top
These characters have everything a character could dream of. Safe options, high pressure, great spacing, good combos, great kill options, and good matchups across the board.
Expect to be able to get to grand finals using only these characters.
They are the top of their class.
Fox
Falco
Sheik

A/High
These characters are strong against most of the cast and have decent matchups with at least one top tier. However, they have some bad match ups either within the tier, with lower tier characters, or in general that hold them back from being top.
You should be able to get to winner's or Loser's finals using these characters, and grand finals with a strong secondary, by and large.
They are 4.0 graduates.
Marth
Peach
Jigglypuff
Captain Falcon
Ice Climbers

B/Middle-
These characters have strong matchups against the lower tiers, but have less desirable matchups against the higher tiers, putting them in a fairly awkward position.
Starting around Winner's semis you have to start out playing your opponent instead of relying on raw matchups if you expect to win.
They are in the top 20% of their graduating class.
Doctor Mario
Ganondorf
Samus
Mario
Donkey Kong

C/Low-
These characters have niche matchups against some high tier characters but preform only decently on their own.
You have to outplay your opponent around winner's and loser's quarters to do well with these characters. Consider instead picking one of these up as a sub.
They'll have to pay their way through college.
Pikachu
Young Link
Luigi
Link
Zelda

D/Bottom-
These characters have hard uphill matchups against most of the cast, but smart play can make them passable in the right

hands.
You'll have to outplay most other players to do well with these characters. They have some decent matchups and can work if the novelty and surprise factor is in your favour
They should look into a craft or trade if they expect to succeed.
Mewtwo
Roy
Yoshi
Mr. Game and Watch
Ness

F/Negligable-
These characters have negligible matchups against almost every other character and their best matchups are against mostly
the other two characters in the tier.
Only use these characters as a joke or in a low tier side event, as what little novelty they have runs thin immediately
after pools.
These three are the class clowns who have no prospect for the future.
Bowser
Pichu
Kirby