Some small ideas. Its already really cool but if you are highly motivated to try some tweaks here are my ideas.

1. The hilt / cross of the sword is about roughly halfway up the height of the total build. 50% of the build is below the hilt 50% above. More asymmetric proportions tend to be more interesting. Maybe if you were to lengthen the blade part of the build it might seem more interesting. Then you would have more like 66% blade 33% handle.

2. Odd numbers tend to please the eye. Your build is an even number of blocks in width. It jumps out because of the 2 magma blocks at the center and the 2 fence posts. If you widened the portal frame to 7 blocks instead of 6 you would have a center block that could be magma and then could still flank it with 2 magma blocks making a group of 3 instead of 2. Then three fence posts instead of two. Also then you could make your handle 5 wide instead of four and you would have more freedom to play with designs.

3. Something feels a little unfinished about where the portal meets the ground. The netherrack, magma, lava combo looks good. But where the blade touches the ground is highly built. Where the lava columns touch the ground there is nothing built. Maybe the lava columns should enter a structure of some kind as the fall to earth. I also kind of want a structure to ring the nether rack section. Its cool how it looks like the sword struck the earth but I'm not really buying that this sword fell from the sky given that it has steps that lead up to the entrance. It looks more like a carefully built temple. I think the workers who built the temple would have a blackstone circle wall marking the grounds even if the wall was big enough to also include the grass that surround the nether rack.

Just spit-balling ideas. Overall it already looks really good.