So in Doom Eternal the Plasma Rifle got a new mod that literally microwaves demons, seemingly heating them up from the inside out, causing them to explode.
One of the largest demons it can do this to is the Mancubus, we'll be using this guy since he likely takes up the most volume due to him being Thicc.
Since this guy is mostly humanoid, to find an approximate volume we can use BMI and then convert, so:
Mass(kg) = BMI * Height^2(m)
This guy clearly has a high BMI for obvious reasons, we can assume a similar BMI to the highest recorded BMI ever Khalid bin Mohsen Shaari, with a BMI of 204.
The Mancubus is also much taller than the normal person, at around 3.85 metres tall. according to the image above, while the image above shows the 2016 Mancubus, the Eternal Mancubus is very similar in size to this incarnation.
Now for the mass:
204 * 3.85^2 = 3023.79kg, easy.
Now we need to heat the Mancubus up enough to cause it to explode.
To do this we need to heat the inside of it causing a lot of pressure, similar to food in a microwave, hence the name.
We don't need to heat up the whole Mancubus though, just enough to cause the explosion, we'll say 80%
80% * 3023.79 = 2419.032kg
Now for the Microwave part...
Specific Heat Capacity of animal tissue is 3500 J/(kg*K)
Humans are made of mostly water, boiling point = 100'C
average internal human temperature = 37'C
difference = 63'C
Total Energy = 533396556 Joules = 9-A, Small Building level
This is done over the course of around 8 seconds:
533396556 / 8 = 66674569.5 Watts, still 9-A.
Due to this being measured in watts any demon that takes longer than a second to microwave should scale to this.
Upon testing this seems to be anything that scales above an imp, so pretty much everything...