Depends on the whether one or both are bound and the velocity of both.

A free electron that slams into an electron in an atom with be absorbed by the bound electron. The bound one will increase its lvl and give off 1 (or 2?) photon(s) to drop back down to its previous state.

Two bound electrons will cause the same process by usually will be bound in both atoms to make them a molecule. (I think this only happens under really high pressure.)

An incoming electron can instead make them both bounce away.

Two free electrons will bounce off each other unless perfectly aligned. In which case, both explode and produce photon(s).

Under enough pressure & velocity and in an excited state, they will bounce each other hard enough that they are can punch into a proton and turn it into a neutron. (Electron Degeneracy collapse.)

It’s been awhile since i really checked into it. To anyone, feel free to correct me and I'll edit this.