This arc has gone on for a long time already, and the intention seems to be to give Lenalee back her fighting ability. However, the existence of a level 4 could cause problems in the future even if this particular one is dead. If the opposing Exorcist can't use power alone but needs that advantage...An issue here is that I do not think Hoshino came up with an Akuma of an entire different level from the ones Bookmen have seen so far, just to make it quick. Once again, who knows? We'll have to see.
Then it wasn't as resounding a defeat... the best recent ones all used tactics. Still, Jasdevi wasn't quite defeated by the power of Krory's muscles.Krory kept on using his blood packs to be on par with Jasdevi but, that only worked until he/she/it found out. After that, he got almost killed, and then he used that odd power-up. Even then, he only managed to survive; Jasdevi didn't die.
I wouldn't say that counts as her actions backfiring, though. She underestimated Lavi, who managed to fool her because of it. No strength involved, either.Rhode lost because she didn't expect Lavi to put his life to that level of risk, nor did she expect his will to be that strong. She underestimated him, and as a consequence, she didn't win.
Awww... I wanted you to say something about Lenalee vs. the level 3 (in terms of power) so I could do a Pokemon analogy. xD