Questions about the Supergirl movie for comic fans - spoilers will be in this, so please only view if you've seen the movie

So I’ve always been marvel fan. As far as DC goes, beyond Superman, Batman and a little green lantern my dc knowledge plummets outside of them. And I have some questions First let me say I thought the movie was a solid 3.5 out of 5. I thought Miley Alcock gave the best possible performance she could. She played the role perfect. The plot I just found dijointed in places. I love all Superman movies. The original Christopher Reeves, Snyders - man of steel and James Gunns Superman. Just so you know where I stand i don’t have a dog in the fight in any of these. With that said. When Snyder made man of steel and everyone was pissed that Superman killed Zod because Superman doesn’t kill. It didn’t bother me I understood why it had to be done. That’s Snyders choice and I respect it. So does Kara follow the same no kill policy in the comics as Superman because I question why she needed to in the movie with a sword nonetheless. Now here’s where my lack of knowledge really drops. The movie her powers seem to be all over the place and the brigand’s I don’t know what if any powers they have besides being alpha bro incel sex traffickers, which was fun to see them get their asses kicked for that reason alone. But the bad guy seemed to be an ant compared to her so that is why I question why he needed to die and by the sword. She’s Kryptonian she could kill him just as easily with her bare hands or just have him imprisoned. Next lobo. I know nothing of him, even though I liked Superman comics I never read one with lobo in it. But I see everyone always hyping him up. I question what purpose does he actually serve it be movie besides just moving the plot forward. Just reading fans accounts of lobo I always got the legitimate impression he was a serious threat to Superman. So I question what makes him a villain and why was he used in the movie?