In one of his blog posts (https://adeptpress.wordpress.com/2015/05/10/a-hero-gets-tired/#more-871), Ron Edwards talks about have fighting is tiring, and how he doesn't see that in comic books after 1980. (Read the post. I found it interesting.)
Champions used to emulate that by having powers and Strength cost END, 1 END per 5 points of power or strength used. A normal person (hah!) had enough endurance to punch ten times, more when you counted recovery in. As a Champions player, I used to find ways to work around END cost, even if I couldn't buy it to zero, I had lots of things on charges or whatever.
Edwards' main argument seems to be that END is realistic--fighting is fatiguing, which I remember from Days of Yore, when I practiced karate. But while comic RPGs don't need to deal with realism (Hello? Flying guys and telekinetic women?), they do need to deal with verisimilitude.
Comics as they are today mostly ignore endurance. ICONS ignores endurance.
If you would find the game more interesting if there were an Endurance kind of stat that made you tired in a linear way, rather than as an arbitrary "He gets away because you're exhausted, have a Determination Point" way--maybe you're playing an all martial artist game--here are some ideas. (This scenario is interesting to me only in an abstract way, so I can't guarantee that the ideas are good.)
Tiring by Default
All powers (including Strength) have the limitation "Tiring." Using a power costs two stamina. If you can fly with chi powers and punch, that's four stamina right there,
It's not linear, but it has the advantage of being right within the rules as written. It also means that fights are going to be short, unless everyone's going to be saving their determination to refresh stamina (or buying Healing or Stamina, if you allow that).
The easiest way is to go for a new derived stat. ICONS has two, Stamina and Determination. We add Endurance to that, and make it five times your Stamina. So Dim Mak has a strength of 5 and a will of 6, he has a Stamina of 11 and an Endurance of 55. But the cost for a power has to switch. Instead, the cost is the point cost for that ability. So if Dim Mak is just punching (strength 5), that's 5 points of endurance. But if he's clearing out the room of mooks (strength with the Burst extra, to get all of them), that's 10 I points of endurance: 5 of strength, 5 of Burst. (Limitations would take away, but the minimum cost for using a power is 1.)
The extra "Zero End" might exist in this version of the system.
This combines them, and lets you roll dice, as well. It is not as linear as the new stat--I haven't worked out the math yet--but can be considerably more punishing than the "Tiring" limitation. You put a limitation--call it "Uncontrollably Tiring"--on the power. Whenever you use the power, roll 2D6 versus the number of ranks of power. If you roll over the number of ranks, you're fine. If you roll under, you lose that many ranks of Stamina, double that many ranks on an 11 or 12.
It behooves the GM not to allow this limitation for powers that have only 1-5 ranks, or to change it to 1d6 in that case.