hi. life remains on storing information (DNA) and usage of this information (protein synthesis) in order to replicate itself in a newer generation.

consequently, a lot of "biocide" we use in medecine target DNA replication or protein synthesis. Another way is to disturb the wall cell (or viral capside) that will make the cell content spread out and make managing DNA or proteins impossible. Ability of a drug to kill a bacteria and not the human carrying it often rely on the ability of the molecule to pass through cell wall and reach its target (so the molecule will enter bacteria cytoplasm and stay out of human cells).

that is for the "chemical agent". strong acid or strong alkali, some chemical reagent (lets say phenol for instance) are able to at least disturb any cell wall and lead to death. they are non selective agent so could be your answer.

there is also of course "physical agent" like electromagnetic wave in UV. they have ability to travel through tissues and break the DNA. Eukaryotic cells have strong mechanism to fix broken DNA but the final result will be a balance between UV exposure and fixing speed.

others waves stronger than UV (X ray, cosmic ray, and for close reasons radioactivity) can act the same on DNA and so are very dangerous to any living beings. keep in mind without the ozone layer around earth, UVs emitted by the sun make life impossible to earth.