Philosophía
"The devil made me do it"
I'm calling it now - H'el [as in House of El, from Kal-El and Jor-El] is a twisted version of Superman. As in, he's a corrupted version of Superman, be it from the future, or somewhat of a clone, or anything similar - either way, they're basically, at DNA, the same person. Maybe from a parallel timeline, where Superman's pod landed somewhere else.
I carefully read his wording in the Supergirl issue, and it ringed that it's being set up for this twist.
It sounds similar to Eradicator but that's just a good red herring - think of him as Kal-El, and then read what he says again.
"I am an explorer, sent on a mission to the stars by your uncle, Jor-El. He was my teacher. My mentor. As much a father to me as his own son. "