Wow there is a lot of saltiness and misinformation going on in this thread.
Killer Instinct is NOT a freemium game. It IS a full fighting game that allows access to a rotating character for free.
It is NOT a PAY2Play or PAY2toWin game. There are no bonuses offered that affect gameplay. There are customization options which can be purchased as well as in game currency which can be purchased to unlock customization options more quickly. The currency also unlocks more stages. Oh, and that currency is earned via playing the game OR by purchasing it with real money if you don't want to play to unlock stuff.
You get the FULL game, with access to use 1 rotating character for free. You can purchase additional characters for $4.99 which nets you the character. You can purchase the Combo Breaker pack for $19.99 which nets you all 8 Season 1 characters You can purchase the Ultra Comb version for $39.99 which nets you the Combo Breaker pack, all the currently available additional costume content, and the original Killer Instinct Arcade game.
If you purchase a character (or 3 if you desire) and decide to buy one of the larger packs, the price you have already paid is deducted so you end up only paying $19.99 or $39.99 TOTAL. This is actually a really cool way to handle it.
As of today, there IS an Arcade Mode.
So for $40 you get a FULL fighting game which includes Arcade, VS modes, and Spectator modes and comes with all of the currently available content of 8 characters, additional costume packs, and the original Arcade game.
Or $20 gets you the FULL game with all 8 characters.
ALL games should have a Single Player mode. I can always guarantee I want to play when I turn on my system. I can't guarantee others will at the same time.