No, the entire point of the contact system is to get Liora NTRed and corrupted. This is not one of those villain is too powerful to drop so NTR is unavoidable type of games.
This game's battles are harder than most but the game can be beaten with the proper strategy without doing any contracts with him. In fact the current update adds Edgar tripping up Rean and harassing Liora in battle just shows how little benefits he brings to a proper team.
As others had said you can power up Edgar if you want but that means weakening the others so Liora is more dependent on him. Of course the opposite is true too. Focus on the couple and he will quickly get left behind. It all depends on how you want to play and if you want to avoid NTR or not.
I’ve beaten every boss on the prior patch on the normal difficulty (I haven’t done the lake yet since the dev himself said it’s not balanced at all), the issue is that if you want to corruption to make sense, the rewards need to make sense, Edgar is a badly statted party member with bad abilities who can’t be directly leveled up like Rean, and quickly becomes irrelevant as he has no progression system of his own. There is almost 0 benefit in ever making a deal with him as many of his deals are debilitating (one really annoyingly high prio one is “must go on a date after a party member falls”) which is basically a straight up day skip but is both low value and frequently offered over actual meaningful corruption increasing contracts.
I know the dev reads this thread, so hopefully I can offer my two cents as someone who actually does pay for each patch
1. Just like SKA has you go into the mind dungeon every day, Edgar should start every day by offering 3 contracts (not just one), impatience should simply increase the value of the deal to show Edgar’s desperation.
2. Edgar needs his stats reallocated, he has massive defense but because he lacks defensive stance he still takes large amounts of physical damage and can’t properly tank, I’d give him some form of passive that increases his dodge chance greatly while he’s protecting targets (feels more fitting for a roguish spell sword than straight tanking)
3. Edgar needs more abilities, going off the fact he seems focused on buffing himself, giving him some “on battle start/turn use buff on” abilities would be great, and open up the contract system a lot more to let you build out his role in the party
4. Edgar needs to steal more often, in fact, I’d make him have a asssainte style ability that makes it clear when he’s going to try to kill steal, with the added bonus that he gets special infusion items unique to him from basic enemies (so he can buff his stats off screen), as well as getting double rewards from boss enemies (to both let him buff himself as well as open more deal opportunities to get the resources back)
just an armchair dev here but I think even a few of these changes could greatly improve the contract system