The Tekken series is one of Namco's biggest properties, a beloved handful of games that helped pioneer the 3D one-on-one fighting genre. Tekken Arena is an embarrassing mobile cash-in, with no 3D element to speak of and barely any portion that could be called "fighting." It might just be the most absurd deviation from the central element of a gaming property that I've ever seen.
Namco calls Tekken Arena a "Massively Multiplayer Online Strategy Fighting Game." What does that mean? It means that this is essentially a text-based RPG, wherein you guide your fighter through a series of ever more improbable excuses for beating the crap out of strangers. Each fighter has a set of RPG-style specifications, plus experience points in a handful of different fighting styles. Until you get into a fight (and again, "fight" is a pretty liberal term here) you're basically looking at a series of short text screens set on static backgrounds from the latter Tekken games.
Then the battle starts. This consists of two sprites, front-facing art featuring your fighter versus your opponent. You can do exactly two things: punch (with a single button) or heal (with a consumable drink). That's it. This is "fighting" with less depth than the average game of Rock, Paper, Scissors. Pressing the button isn't even required - your fighter will attack automatically if you do nothing.
There are social features in the game, but if there's a true multiplayer element in the horrible interface and various bloated game modes, I can't find it. The only real point to the game appears to be increasing your fighter's arbitrary stats and recruiting Tekken characters as apprentices, then customizing them with outfits. I suppose you could say that getting through the story is the point, but show me a fighting game with a compelling story and I'll show you a gamer who needs to get out more. Eventually you'll run out of money, stamina, or both, inevitably leading you to pointless grinding or spending real money on in-app purchases for replenishments.
Tekken Arena is a lamentable excuse for a title, a textbook study in how to completely abuse source material and insult mobile gamers in the same time. It's also compatible with almost nothing, but at this point, that's actually more of a blessing than an issue.