Opening statement: I have over 250 games owned on Steam (not including F2P games), and this is the only one worth a negative review out of all of them. Before you waste your time with the "helpful" reviews, most of the "helpful" positive reviews for this game have very little time spent in the game, when one of the biggest detriments to this game is the completely repetitive nature of it.
This is without a doubt one of the biggest disappointments for a smash bros type game I have ever seen. There is no difference between any of the characters except how they look as the only thing you do is either jump or use a power-up. There is no such thing as a "move" in this game, which is a complete insult to the genre. Both the control scheme and combat are completely terrible, as even with the so-called jokes for "power-ups" the game devolves into who can jump better.
What makes the awful control scheme even worse is the complete lack of any option to change it whatsoever. Think of the game as Smash Bros with absolutely no moves, on items and jumping on your opponent's head. The closest comparison I can make is Towerfall Ascension, only without the arrows or the map overlap. The different game modes do nothing for the game either, as the gameplay does not change. Yes, the game does offer a significant challenge, but it is completely repetitive and dumbs down the genre to such a point that takes the entire amount of fun out of it.
The challenge mode is a joke, the first level is literally sitting in the top right corner waiting for enemies to jump into you. 90% of the strategy in this game is to get the high ground and camp it. Even as you progress farther, it still remains exactly the same kind of thing, even though the maps and available power-ups will change. Every single "challenge" comes down to the same thing: find the right way to cheese the map with the high ground and avoid getting spawn killed.
For a genre that prides itself on having complexity of combat, this game is an utter disappointment from its incredibly dumbed down three-step approach: 1. Take the high ground. 2. Hold the high ground. 3. Win.
TL;DR: If you're looking for a good smash bros type game on Steam, this is the opposite of what you want. This game is a waste of money and a joke for the genre, as it is without a doubt the worst game of its type I have ever seen. If you made the mistake of wasting your money, just idle to get the cards and never touch the game again. I wasted more time than I should have on this piece of garbage to see if it would get any better as time went on... it only got worse.