Hel

If you look at the list of all runes, you can find out the cube recipes to create a rune of one level higher than Hel. Here are the Hel attributes:

Rank: (r15)
Weapon: -20% Requirements
Armor/Helm/Shield: -15% Requirements
Ilvl: 33 Clvl Required: 0 (the only one that they aren't identical)