The logo on the left has many pixelated lines, this is especially annoying near the red parts.
On the top left side of the logo, the two grey fragments are closer to the center than the red/pink ones.
The text's white blur leaves to be desired, same for the font of the "hacking to the core" text.
If you want to improve further, you need to be careful about shapes and you must put additional effort into details.
Right about that, tools like alpha selections aren't great to cut something that needs to be well defined and exposed, like for any logo, i think that's how those overly sharp or thin lines happened.