A Useful Way To Improve Poppy

Keep everything the same, but change the ultimate.

Instead of Poppy playing golf, sending them towards their nexus, or the quick knockup tap, the ult does a direct knockback only.

It does bigger damage than her ult does currently (it needs to), it knocks them back 475 units (the distance of her E, or adjust it to something else based on balance), and it stuns them for various durations depending on rank ONLY IF THEY COLLIDE WITH TERRAIN. Therefore, this could create combos for her and her teammates, and it would be more useful than it is now. Now, it can knock them out of danger, which is completely useless. With my suggestion, you could Still knock them out of danger (if you aim well), or knock them into a wall for a setup for a kill or a tactical retreat. Because the distance of an ultimate wallstun is variable and likely out of Poppy's melee range in some cases and is up to 475 units, the stun should be up to 2 seconds depending on ultimate rank, much like max rank E is a 2 second stun (or pick a different duration based on balance) . I therefore envision in a 1v1 a Poppy Ultimating someone into a wall (or even towards a wall) and subsequently wallstunning with E and or chainstunning with E should the R already stun them. I could also envision Poppy ultimate stunning someone towards a wall in 1 direction, and then E stunning a different target in another direction.

either way, OP or not, this is more usefull than the current useless ultimate.

TLDR: Change her R to be potentially long distance knockback that interacts with terrain with a stun, helping set up a subsequent E stun or a team play. Edit the animation to be an appropriately tough representation of the new animation.

Also, the current ultimate does something similar with its knockup, but the knockup lasts 0.75 sec, not 2 sec. I can't imagine increasing the duration without a ridiculous animation. Since the airborne golfing animation sends them to safety and is useless, and since we depend on the 0.75 second knockup for combat usefulness of the ult, and since making a knockup last longer would have horrible animations (where they go off screen and can't be seen while airborne or something), changing the ult to a knockback with a 2 second stun upon colliding with terrain would be able to be animated, would increase the combat usefulness of the ultimate, and would be viable thematically with a hammer wielding yordle.

Second Edit:

Perhaps if you make it sufficiently strong as described above, she has lowered resists for maybe 1 second after swinging her hammer on ultimate like a baseball bat, soon restoring her normal resists when she recovers her stance. Therefore, she has appropriate risk and reward and tactical ideas to consider.