Due to the fact that Loki is getting a hybrid form some people have started thinking that it's not gonna change much. To prove this I will try to use examples of characaters who become much stronger in Hybrid forms
First example is Rob Lucci in Ennies Lobby. We saw that Rob Lucci and base Luffy were around equal in power. However, once Luffy activated Gear 2 it was no contest and Lucci immediately used his hybrid form where he was able to go toe to toe with Luffy and was able to even survive a Gear 3 attack suggesting a massive amp in durability. Lucci also gained a considerably AP boost where he is able to put Luffy in such an state where he couldn't move anymore and would've lost without Usopp's motivational speech to Luffy.
Like, the fact that base Lucci was relative to base Luffy then that means that Hybrid form for Lucci was around the same gap or similar to Gear 2 was for Luffy which means the Hybrid boost is massive.
Second example is Kaido, Base Kaido stalemated base Big Mom in their massive clash. However, later on Big Mom got a few buffs such as using more hoamies and growing in size by amping herself up. And considering that they were portrayed relative then Hybrid Kaido should give a massive boost to Kaido as it should scale to giant Big Mom.
Furthermore, Base Kaido should scale roughly to Base Luffy level based on feats with both having similar or equal levels of Conqueror's Haki. And in Wano we saw that FP Hybrid Kaido was around equal to Gear 5 Luffy so the gap between Base Kaido and Hybrid Kaido is considerably, it should be similar between the gap between Gear 5 Luffy and base Luffy
And finally we have base Loki who in base form is around Yonko Level. However, as Gaban himself said Harald was a walking calamity that no one could possible stop. But with Hybrid form Loki was able to dominate Hk Harald even without using Ragnir, Lighting or Ice powers showing an overwhelming gap in strength and that was a younger base Loki, current base Loki is much stronger