The spell we saw from Luslec is attrition, rather than a sure hit, and it would not work against Baam as easily for this reason. But I can't say the same for Lefav's bullet, for instance. Baam needs to react to use those broken powers or immense battle IQ, when you ambush him and one-shot, I am not sure, he is THAT durable. He needs another power up to be not one-shottable.
IIRC, the Luslec spell would attack the person unless the person dies. The spell won't let go of its resentment unless the person it gets cast on dies. Hence a sure-hit kill. It's just a shame it was shown against Urek.
If Dumas was not able to one-shot Baam, I'm pretty sure Lefav's bullet won't.
Baam is not only blessed by Shinsoo, but he's also pretty blessed in luck. Every time some shit happens to him, something else happens that enables him to get out of that situation. We have seen this countless times.
This brother was able to survive Gustang's flame, which no high ranker was able to do. That's durability. (I know Traumerei helped in the end, but he was hanging on; even Gustang was surprised.)
In fact, I would argue his battle IQ is shown to be pretty peak in the series. How do you think he survives fights against high rankers?
He's pretty reliant on his teachings from Ha Jinsung in martial arts. The way he uses reverse flow control in his fights and then his wave control abilities is just a testament to his IQ. Just see his fight against Lo Po Bia Ren, who's Jahard's selected high ranker.
What he needs is consolidation of his powers. This is what V is teaching him.
