There are plenty of supposed Steam Deck killers available in the portable gaming space, from the Asus ROG Ally to the Lenovo Legion Go and all the Ayaneo and ONEXPLAYER devices in between. But none of them have managed to outright slay the dragon that is the mighty Steam Deck yet.
I have both the Deck and the ROG Ally. The Deck feels like a complete product and is great to use. The Ally is impressive when pushing over 100fps on relatively demanding games, but the overall user experience is garbage. Windows is a terrible platform for a handheld. I dual boot it with Arch now and can run gamescope session for the Deck experience, but I just recently figured out how to use ryzenadj for TDP control so I could see anything near full performance. The buttons don’t work for navigating the Steam UI when in game. Audio requires a UEFI override. It’s still a better experience than Windows but nothing compared to the “it just works” console style Deck experience. The Deck hardware is more ergonomic and has better designed controls too. Trackpads are incredibly overlooked.