The Fixe hanger is currently the strongest hanger available. These will accommodate two carabiners, has three dimples to help prevent spinning and is cut from 4mm A-304 stainless or plated steel.
Strength Plated Steel: 25kN
Fits up to 1/2" Rawl bolts
12MM version fits Fixe Triplex bolts
Strength SS: 30kN