I think the Thinkpad X130e with the AMD E-240 CPU. That processor, really, was the bad part. Every little single thing you wanted to do was absolutely CPU-bound, even when it was contemporary and new (c. 2011-2012). The amount of time I wasted waiting for the fully hammered CPU to do literally anything was too much.
I bought the laptop used because I figured a tiny Linux laptop would be great. And other aspects of it were fine, such as the display, keyboard, trackpad, build quality, etc. But that stupid CPU totally killed the device. Such a regret.