You shouldn't need BP or Karma to create a superior NPC - simply assign that NPC whatever skills, Attributes, and gear make sense.
There are numerous ways to have a "superior" NPC. Obviously, you can take a PC as a starting point and make a character who is better in some way, or multiple ways. Or the NPC can be superior like the Tir Ghost NPCs in the book are - by having a superior breadth of skill and a lack of any glaring weaknesses. And superior NPCs are not limited to rival runners - they can be superior because they have massive resources to bring to bear, or have lots of important contacts.
Only the first type could really hope to go toe to toe with the whole group (and even then, not likely - a group can usually take out an individual fairly easily), but that's actually fine. Shadowrun is a more tactical game, and NPCs should succeed with clever plans, not by being no-selling, end-of-level-boss types.