Nukes will solve any problem that requires a considerably high amount of energy being released in short time, which I figure could be about 10% of the questions in science-based.
We have already mathed out the amount of energy you need in order to disassemble a human body into molecules before in these questions:
And here is the source for the estimated amount of energy required to vaporize a person. It is around three gigajoules, which is what you get from a single metric ton of TNT.
That single ton of TNT would only fully vaporize a person in very ideal lab conditions though. Most likely you would get chunks that could still be used for DNA identification. What we need is to dial things up to eleven.
The smallest nuke ever made is the W54. It fits into a backpack specially designed to encase it, as seen in this image from the Wiki:
Notice the fire extinguisher, for size comparison. It is quite feasible for a black ops team to carry one or two of these backpacks.
The maximum yield for the W54 is about 1 TNT kiloton equivalent. For comparison, an accidental, disastrous, non-nuclear blast of that yield happened in 2020 in Beirut:
The blast was also felt across Turkey, Syria, Israel, the West Bank and parts of Europe, and was heard in Cyprus, more than 240 km (150 mi) away. It was detected by the United States Geological Survey as a seismic event of magnitude 3.3, and is considered one of the most powerful artificial non-nuclear explosions in history.
The explosion overturned cars and stripped steel-framed buildings of their cladding. Within the port area, the explosion destroyed a section of shoreline and left a crater roughly 124 m (407 ft) in diameter and 43 m (141 ft) in depth.
There is footage of the blast, though it may be understandably distressing to watch.
If you activate a W54 warhead upon a fallen comrade, you will fulfill the hard requirement in the question about body and equipment being turned into something not recognizable. It is also a non-magical solution that is feasible with less than current technology, since the W54 is an invention from the 1950's.
As a bonus, you can also deal considerable damage to the enemy side. The mininuke in your possession might also be a deterrent against retaliation or against being chased when you retreat.
Last but not least - you should preferably be able to trigger it remotely so that you can put some safe distance between you and the teammate you wish to evaporate. You can figure out possible safe distances by using the NUKEMAP (don't forget to set the yield to 1 kiloton before you detonate). For most cities, you should be a couple neighbourhoods away just to be sure.