"IT'S OUT OF CONTROOOOOOL!"
So, the dice have fallen, your Druid has chosen, you have adequately played to find out what happens. Now it's time to shift focus to some of your other responsibilities as GM, like portraying a fantastical world and filling the players' lives with adventure.
I'm going to explain how we get there in just a second, but while the following sections grab your eyeballs I'd like you to have a certain concept percolating around in your skull - the thing the Druid actually set out to accomplish is being produced by a machine, and the spiked-hairin'-est white-coatin'-est person you can imagine just charged breathlessly into the scene, pointed shakily in its direction, and screamed, well, you know.
An Introduction: Success, Failure, And the In-Between
You've mentioned you feel bad coming down on your Druid because they rolled a 10, and a 10 means success. This isn't the first time I've heard people say this, and I know where you're probably getting it from.
The results always fall into three basic categories. A total of 10 or higher (written 10+) is the best outcome. A total of 7–9 is still a success but it comes with compromises or cost. A 6 or lower is trouble, but you also get to mark XP.
Each move will tell you what happens on a 10+ and a 7–9. Most moves won’t say what happens on a 6-, that’s up to the GM but you also always mark XP.
The first paragraph there is just an overview - the second paragraph is the important part. Each move will tell you what happens on a 10+ and a 7-9. You don't somehow get a minor version of the one downside you don't pick on, say, Bend Bars, Lift Gates on a 10+ just because you get a success. It's just worse on a 7-9 because something also happens in addition to it. Similarly, if you're trying to shapeshift into a tiger and get a 7-9, you're not somehow a rubbish tiger because it's a 7-9. You get less hold, which means less time doing important things as a tiger before you need to take the risk on shapeshift again.
So, the downside on a 10+ is just as potent as the downside on a 7-9. It's just the only thing you have to deal with, instead of one of two.
Nature: Red In Tooth And Claw
So the thing about nature that people sometimes forget about is that nature doesn't care about anyone or anything. The only thing nature does is act natural. And, well, predators are natural. Every freaky swamp plant that kills things to get the necessary salts out of their bodies? Natural.
Wildfires are natural. Avalanches are natural. Earthquakes are natural. Hurricanes are natural.
And now you've given all those natural things a will and a direction and you've lost control.
And this is where the machine thing comes from. Like a machine, nature follows its own modes of operation. Like a machine, it does its task and it doesn't care for the side-effects.
The move may be called Elemental Mastery, but the Druid isn't really attaining mastery. They're setting a spirit on a task for a reason, and the thing you need to think about as a GM is the reason. What can you do to accomplish that, but complicate their lives as much as you want because they chose to lose control?
That's a golden opportunity there, no mistaking it. The druid called up an uncaring spirit of the elements and chose to lose control. So make a move.
Make a move that makes the world seem fantastic and gives the players an adventurous way to accomplish their original task.
The Druid wants it to stop raining around them but loses control? Maybe the rain just gathers above their head in a giant, pulsating orb that sloshes about as they move, and occasionally bits of it spill over the edge, sending great splashes of water down to the forest floor. Now they're going to need to walk carefully as the orb gets larger and larger.
Maybe the rain all starts vectoring off in a different direction and now you've got a water cutter making a nice clean line in the landscape for anything that's tracking you to follow.
Maybe it starts turning back into a cloud when it gets near the ground and the Druid's in a rapidly thickening fog bank.
The Druid wants wind to fill the ship's sails? Great, it does. And then it keeps going, and going, and one of the restraining ropes on the sail snaps and flails around on the deck like a giant's whip.
Or maybe a huge wind blows up behind the ship, and now the ship is headed to its destination atop a fifteen-foot-high wave.
The Druid wants an earth elemental to make a hole in a wall? Right, it merges itself into the wall and then flexes, tearing itself apart. Now there's a hole in the wall, occasionally interrupted by the twin earth elementals jealously lashing out, grabbing bits off each other or trying to knock them off.
It's all going to revolve around giving the druid what they want, but on a timer or with a side-effect or complication that stems from the loss of control that they chose to have.