While not connected to the current discussion, one character that I believe could truly shine this time is Carol Danvers aka Captain Marvel...while avoiding everything Disney did wrong with her believing themselves owners of the "truth".
First of all, I can still see her as the best match-up from the Avengers against Thanos. And this could be explained if she gets her powers from more than One Infinity Stone. Like 2 or 3. That would explain better her "OP-ness".
But this time, there are secondary effects by using her powers:
I thought two possibilites that could work on their own or together.
Whenever she activates her power, it feels like "inserting a hot iron rod into her spine". That means she would be forced to grow from that pain, not being capable of using her true might without suffering too much pain each time.
And/or her "power output" can be adjusted depending of her needs, like the Kaio-ken from Dragon Ball Z for those familiar with it, which effects include:
"It is a technique that multiplies the user's
ki for a "heartbeat" - thus increasing their power and speed and enabling them to inflict serious damage to opponents who are considerably stronger than them. However, the downside of the Kaio-ken is that it takes a heavy toll on the user's body, making them more vulnerable to enemy attacks."
"There is no change to the user's physique, but the enormous stress of the technique can result in increased blood pressure, popping out veins and swelling the user's muscle mass. The technique can also generate large amounts of heat from the user's body whilst being activated, creating steam rising from their body."
In overall, Carol gets to be one of the most powerful characters in the MCU, capable of going toe-to-toe against Thanos with his Gauntlet (even if only temporality and briefly) with at the cost of extreme pain every time her power is used and/for her body gets damaged by the strain.
PS: Oh and certainly let's avoid introducing her in a prequel/before the current movie events. We don't have that MASSIVE PLOTHOLE again...