I feel it hurts Zard more then anything. But that's mainly because my style of play relies on observing, speculating, and reacting to precise movements so I'll be exactly somewhere I want to be and getting the punish. With lag, my movements get sluggish, predictable, and often whiffing an unsafe option where I got the read, but the Wifi gods just said 'NOPE' and then I suffer a bunch of lag causing a free punish. Kind of irritating really
I think people mainly get salty when they loose so they start complaining about the character and condition instead of improving their game.
The truth:
Lag in a sense 'benefits' every character or 'cripples' every character depending which way you view it.
Universally long lasting hitboxes such as projectiles will benefit since it requires just a press of a button to be there. Meanwhile, the opponent has to time their shield.
Throwing out random Smash attacks is also benefited through lag. One will eventually hit so might as well use all of them until one hits, amIrite?
Rolling. Ugh, this is rather stressful. The oppenent needs to press a single button, they're invisible. The one that's reading their over-reliance of rolling needs to use their move X frames earlier then usual. And that X can very depending on how many frames of lag there are making timing for this very inconsistent.
In short, those that can throw out quick Smashes, have good rolls, and lots of projectiles and the player who chooses to use them are going to benefit heavily. This makes characters such as Link, Samus, Mario, and Yoshi very frustrating if the opponent plays like this.
Those who are trying to utilize good fundamentals are most likely going to get frustrated if the opponent has poor connection to the internet. Pretty much, the better you get, the worse you get.