Nvidia and Intel have both been proven to partake in anti-competitive practices.
Nvidia's PhysX physics libraries and "Made For Nvidia" partner programs are example of this.
If you're running a game using PhysX on AMD GPU's, the PhysX calculations get placed on the CPU which can degrade overall performance. Kind of underhanded IMO.
Then there's Nvidia and Linux: Nvidia refuses to open-source any of their driver components by claiming they are licensing them from someone else. Whereas the newest official Radeon drivers: AMDGPU-Pro, are open-source now.

Then there's Intel, who paid millions of dollars to OEM's like Dell/HP not to give much attention to their AMD-based products.

AMD on the other hand was approached by an Intel engineer with trade secrets, and told Intel about it rather than buying them.