Demigras energy, not at his peak even, is warping all sorts of timelines and causing the multiverse to overflow.
https://imgur.com/a/h444t
He plans to create his own history or "new world" from nothing after everything is destroyed.
https://imgur.com/a/4WibN
Demigra's energy trancends the DBH multiverse and spacetime and enters the real world, being able to destroy both.
https://imgur.com/a/6Vcla
Demigra controls Trunks for one, and Trunks completed training with beerus and Whis and can physically hurt Demigra and help in the battle.
He also almost cotnrols The pattroler, who can go toe to toe with him in power, until Trunks and kai of time steps in and helps.
https://youtu.be/dC58Yj4oCg8?t=350
So he can control people at his level.
Demigra one shots, detransforms and immobalises the pattroler and SSJ3 god ki Goku, both of whom can physically stand up to him in theinal battle showign he can supress adn nulify power and skills of those on his level. Also beat as a SSJG had his powers nulified until he could purify Demigra's evil energy, and Beat is one of the ones who defeats Demigra in the end showign he is on his level.
https://imgur.com/a/BEqoT
Demigra's attack "time shackeles" is a move he uses on pattroler during battle that traps them and damages them, it looks similar to what was used on toki toki minus eating them to. So sealing is literally one of his battle attacks.
As for absorbing he does this to Toki Toki who is able to reset the multiverfse after its destruction, create timelines and vito Dmeigra's power. That alone is impressive since Toki Toki can't escape. Also like was said against the pattroler time shackles seems very similar to this, minus the eating them part.
Demigra goes from being hurt by base god Goku, to outclassing SSJ3 God ki Goku, that is a massive instant boost. And that happens within seconds from one battle to the second one where even his base one shots Goku and pattroler. That is probably the biggest near instant leap in power, but he has multiple moves and statements to that he gains power from gatehring energy or kiri over time, absorbing clones, absorbing battle energy, some things in heroes that are specfic boosts when winning exchanges or taking damage etc as well. So he can jump from having trouble with base god ki Goku to outclassing SSJ3 God Ki Goku in a moments notice.
The issue I have with flowey save and load is, they still do rely on making new tiemlines and those sadi timelines still existing for him to load after being destroyed correct? SUre he can survive the multiverse being gone, but if he himself were destroyed as well as all existing timelines then he has nothing to come back from, adn Demigra if he can best flowey can certainly erase the timelines even if tehy are outside the multiverse while he is at it. So there would be no save to load from.
As for Frisk though, I agree he nuked the saves, but I don't see how your saves are equal to a full multiverse, and also I don't know if Flowey > Frisk, is tehre proof of it?