An example is that MC was alone with a girl (Sybil) in a dungeon after being separated from the group. Sybil gets lethally poisoned and is saved by MC. In addition she gets to hear some interesting things about the MC, some of which seems to even inspire her. You would think she would somehow get entangled with the MC especially after knowing that she is described as a "villain" with an ability to subconsciously bend fate to favor her but nope after it was said she survived there was no mention of her. A character like her who craves excitement just disappears in the story for several chapters after witnessing such interesting events is just unbelievable.

One example is how MC got the viscouelastic metal. It was being auctioned as it was being paraded as Baldur's kryptonite which is the Mistletein and MC had proven it was a fake. He was rewarded by his father since he prevented him from using Gram (a super important sword) as payment for a fake but the reward MC decided on was to have a good look at Gram to replicate it using his ability. As for why he also got the fake Mistletein, I have no idea. Did the Zodiac guy reward MC for showing such bold action? Did his family win and gave it to him? Did every participating family just gave up after seeing it is a fake and just let MC have it?

I honestly have no clue as the story doesn't bother telling me

In chapter 8, Quinie and MC coincidentally met and had a bet whether a painting in the museum is fake or not. In the end MC won and Quinie had to give MC a lot of money but this entire thing was not mentioned or even hinted to have happened in any future interactions between these two. Hell when these two met each other again they said that the last time they have met was in the auction of the fake Mistletein (which happened earlier that when they met at the museum).

The protagonist decides to return to his original world. There are things mentioned, like Loki being from another world, but we never get to learn anything about that world or whether it's the same as the protagonist’s—leaving us with unanswered questions. Beyond that, the final war felt anticlimactic to me, but the worst part, I repeat, is that the protagonist decides to go back to his original world, even though he barely talks about his family and I don't even recall him mentioning any friends there.

Also, despite the many women interested in him, he doesn’t end up with any of them. He makes Selena cry, Ellodi cry, and basically hurts every woman who had feelings for him, and acts like it’s nothing. I’m not saying there had to be a romance, but then why did the author create so much romantic interest around the protagonist if, in the end, he doesn't even share a single kiss with any of them? Why include such a disproportionately large number of women around him, and give almost all the narrative depth to those women, if he’s not going to end up with any of them?

Honestly, the ending is incredibly disappointing. (Not to mention the whole thing about the clock and the rewards, which is completely dropped halfway through the series and randomly brought back at the end without giving him anything. Or how he absorbs the mana of the nine realms without consequence, and then just uses that mana to kill the goddesses of fate.)

Example;

MC is previously stated to be capable of conjuring a umm legendary grade artifact for only 3 seconds.

Some nobility hating madman, attacks the MC; MC is heavily injured and exhausted, female heroines come to rescue, they are incapable of eliminating the opponent for reasons so now obviously this happens:

MC -once again might I add, is heavily injured and exhausted- is now suddenly capable of not only casting divine-ranked runes, but also conjuring divine-ranked weapons while having enough time to have a deep conversation with the heroine.

Okay, it's known knowledge that royal family can see future, however, it is mentioned that none of princesses can use it. Even the existing user, the Empress can only really vaguely intuit the future

MC is f*cking dying after pulling his regular shounen bullsh*t in front of princess, all of a sudden it's said that the Princess has potential as the greatest healer and through the power of bullsh*t (i.e future magic) the princess heals the MC from near death.

Eg: The Empress personally going with the MC, without any guards, to the base of a suspected traitor. Even if said traitor is one of her daughters, she must have some sense of danger.