In later seasons we learn that
- Meliodas's power level is ~3370, and all the Sins's powers are above 3k, while Gilthunder and Howzer are somewhat below 2000
- Grey and red demons are inferior demons, unlike superior Ten Commandments, Chandler, Cusack and other powerful demons. Basically, both of these types are somewhat like privates
- In season 2, Gil, Howser and Griamore (with combined power < 6000) successfully hold their own against a full-scale grey demon until Hedrick defeats him with his druid power.
- Also in later seasons other knights pretty much manage to fight armies consisting of the same red and grey demons, which points that these demons are not super tough like Commandments.
Based on all this stuff, how come Hendrick (who is basically a human under a spell with demon blood) was powerful enough, that 5 out of 7 Sins (with combined power of somewhat like 3k * 5 members = 15k) and a buttload of knights weren't even able to properly fight him and were massively killed?
I'm looking for an in-universe explanation, out-of-universe he's got plot armor
