Deal two decks straight into ten tableau piles, skip the stock, and untangle runs for a friendly 85% win rate.

Double Scorpion Solitaire plays like Scorpion Solitaire but with two decks, and every card is dealt out at the start, so there's no stock to fall back on. It's rated simple, with an 85% chance of winning, and success comes down mostly to skill: read the board before you start moving runs around.
If you like the two-deck format, Triple Scorpion Solitaire pushes it to three decks for an even longer game.
If you run into anything odd or have an idea that would make the game better, please contact me.
Have a good time playing!
10 tableau piles: Built down in suit, and a run of cards can be moved as a group even if it isn't in strict order. Empty piles can only be filled with a King, or a King with cards stacked on it. To start, the first four piles get 11 cards each and the rest get 10 cards each. The bottom four cards in each of the first five piles are dealt face down; everything else, including all of piles six through ten, is dealt face up.
There are eight foundation piles, and they stay hidden off-screen.
You can't move single cards to the foundation. Only once you've built a complete run of thirteen cards, ace through king in the same suit, can you send it up as a group.
Once a run reaches the foundation, it stays there. You can't bring it back into the tableau.
Ten tableau piles hold the cards, shown below, where "D" marks a face-down card and "U" marks a face-up one:
A card can go on a tableau pile if it's one rank lower and the same suit as the pile's current top card. So the only card that fits on a 9 of spades is the 8 of spades.
Any card that isn't covered by another card is free to move to another pile where it fits, or up to the foundation as part of a finished run.
Only a King, or a King with a run of cards on it, can fill an empty pile.
You can also grab any face-up card, along with everything stacked on top of it, and move the whole group to another pile where it fits, even if that group isn't in strict suit order itself.
The goal is to sort the whole tableau into eight complete runs, one for each suit, each running King down to Ace, and send them all up to the foundation.