Your own link states that "in part" definitions may lead to highly subjective conclusions.

Yeah, that part means that you don't have to kill every single Palestinian in order for your deliberate eradicative campaign to be a genocide. It doesn't mean "killing any part of a people is genocide" 🤦

By this measure, the death penalty in the US would be considered genocide "in part" (especially if the judge, jurors, or clerks are mostly white and the executed person is of color, so as to establish that a "group" is targeting another group). A person acting in self-defense with a resulting death to the aggressor may also fall into the genocide criteria

Nope. Of COURSE not. I'm almost completely convinced that you're arguing in bad faith. That or you're extremely literal-minded AND not too smart.. These are not difficult concepts for most people to understand and differentiate once it's pointed out to them.

If Israel is only intent on destroying the Hamas terrorist organization

Yeah, that's a negative. They're trying to kill or displace away from the area every single Gazan and they're already at over 90% displacement.

it is technically a political party, but they broadened their horizons on October 7th, I guess...

No, it's a terrorist organization masquerading as a government. Critical infrastructure such as schools and hospitals are de facto run by UNRWA, not Hamas.

and not the whole Gazan/Palestinian population

That IS their actual target. Your Hasbara hypothetical isn't helpful.

could it really still be labeled as genocide?

In that purely hypothetical scenario, whether it's still a genocide would depend on a number of factors, including whether or not they take great care to avoid civilian casualties and only target known Hamas targets. They don't, never have, and never will.

As I said, some people will even say a single death may be genocide "in part,"

Nobody not arguing in bad faith, profoundly confused/ignorant, or colossally dense. Since I gave you the definition, it's either bad faith or stupidity in your case.

so this widening of the definition just weakens the term, unfortunately.

No, it's not a widening. It's a specifying that you don't have to successfully eliminate everyone for it to be a genocide. A distinction that most adults not arguing in bad faith have no trouble comprehending.