Talk:Jugem/@comment-187.253.146.53-20151025052135/@comment-27099834-20151025054155

1. Ainz deliberately raised Goo as a weak undead because he only wanted to test the village and not annihilate it.

2. Goo was overwhelmed by Jugem + a few other goblins ie wasn't a solo kill by Jugem

3. Jugem leveled up during the fight due to shounen's 'power of friendship' and 'believe in yourself!'

Just a few reasons that could explain it, but 1 seems most likely.