If you scroll through the above list, you’ll notice that quite a few characters have RNG-related (RNG essentially means random) aspects to them. Peach’s turnip plucks are randomly decided, as are Villager’s up and down aerials. Yoshi’s Island (Brawl) has the support ghost and Shy Guys that randomly show up to help or hinder the match, and Dream Land 64 chooses which direction to blow randomly if there’s an even number of players on either side. There are several instances in the game where the outcome is chosen by the game and not by anyone’s level of skill.
After a while, you’ll stop and wonder why we’re okay with that. Games with too much randomness end up like competitive Mario Party: even if you win, we all know you just got lucky. Games with too little randomness end up like chess: if you win, everybody knows that you’re brilliant, but it took you fifty years to get to that level. Some people like to have fun for the sake of having fun, and they choose Mario Party. Others want to be judged entirely on their skill, and they choose chess.
The game of competitive amiibo is neither of those choices. Competitive amiibo is built off the back of Smash 4, which is one layer of randomness. But amiibo themselves are also very random! It’s a dirty little secret that wasn’t exactly forthcoming in Nintendo’s initial marketing campaign.
Let me prove it to you. Take two already trained amiibo, let’s say they’re level 50 for simplicity’s sake. Scan them into a game. Place them on Battlefield or an Ω-stage, and write down the rules format, stage and the ports you placed them on. Have them play, and then write down who won, how much damage was dealt, and how long it took. You can write down more stats if you like, but at least have those numbers.
Once you’ve written them down, don’t save your amiibo. Turn off the console at the results screen. Turn it back on, and start up another game. Replicate the rules you had the first time, down to the stage and the order you scanned them in on. (The order and ports you scan them is actually important because of port priority.) Now check the results.
The same amiibo may have won, but I guarantee you the stats gathered will be different. Why? These are the exact same amiibo scanned into the exact same console under the same circumstances. How could it end differently?
It ends differently because amiibo are partially RNG. You can influence them to a great degree by training them but no amount of training can ever completely control them. That’s not to say there is no point in training the amiibo; you can still have a lot of fun with it, and the competitions are kinda neat too. To suggest that there can ever be a 100% certain winner, though, is folly. You never know how the RNG can end up.
In summary, amiibo competitions rely on two layers of randomness to function. There’s the layer found in the actual game of Smash 4, and there’s the layer of randomness that dictates how amiibo behave.