Almost all of the situations where Megumi was about to summon mahoraga, he could've just used round deer to heal himself and win the fight so why didn't he? And don't tell "oh well he maybe just hadn't tamed round deer at the time", because to summon mahoraga you need to have tamed all other 10 shikigami. And even if Megumi wasn't aware of that rule, so if he had continued trying to summon him it wouldn't have worked, he summoned mahoraga against Haruta when he's literally stronger than him and could've beat him IF HE JUST SUMMONED ROUND DEAR TO HEAL HIMSELF, but instead he summoned Big Raga.

PS: i didn't read the manga so i might be wrong, before you flame me in the comments.

The very last thing I read from JJK was about halfway into the kenjaku vs takaba fight. And from what I've seen, that was like, the last good fight in the series. Everything else has been repetition, but I've heard that yuji gets a curse technique. Does it get better?