Cutting into your achilles tendon is bad enough and if you do manage to do it there is a high possibility of hitting that artery. Cutting an artery is never a good thing and wherever you hit it there is a good chanch that you can bleed out. Granted, it would take bit more time to bleed out from a small artery in your foot than it would to bleed out through your femoral artery, which only takes a couple of minutes if not treated immediately, but, any artery will cause severe bleeding and can cause death fairly quickly. If you cut that artery and it recracts up into your leg you're in big trouble even if you don't pass out because it will still be bleeding. In that sense, cutting your achilles tendon could easily become a life or death scenario, as can a broken or dislocated ankle, or knee for the same reason.