Here are a couple chain axe designs to convert the new CSM kits into Khorn berserkers. I suppose they can also be used for the terminators.

The first weapon is a simplified version of the one that comes on the Shadowspear box, since the full think would look a bit too detailed for you normal guy. The second one is an original design inspired by the older, flatter Khorne Berserker ones.

There is also the closed armoured hand and handless weapons in case anyone wants them.

I'm still new to 3D design so these probably have way more geometry than they should. Most of the detail prints fine on the Anycubic Photon. I've printed only one of them and I'll upload photos when I can. They print fine by placing them head down and using supports only on the flat parts parallel to the buildplate. I also used a single support on the index finger but I'm not 100% sure it's necessary.

Edit: After printing the ones with the hand on the lower part of the handle I realize they seem to be a bit too long. Since they were based on the aspiring champion of shadowspear and that appears to be almost a two handed weapon. I'm going to make a shorter version of the handle to see if it looks better