The giant said to himself, "This killer is impressive. Too bad he embarked on the wrong pathway."
He was impressed, but no matter how in awe he was of Legion-2, he wouldn't stop trying to seal Legion-2 forever. Just like he said earlier to Legion-2 when he found out that Legion-2 was also an angel, there are worse things than death. He wants to make that promise come to pass, and he is willing to do so regardless of his admiration for Legion-2.
But because Legion-2 was struggling so much, what should have taken five seconds to complete was extended into a minute. The immediate repercussion was that he was burning through divine energy quickly.
He can recover divine energy if he wants to. He can just let the god of guardians resurrect him again. But if he does that, he will have to die. This will break the white light since the Seal ultimate ability will be deactivated once he dies. So Legion-2 will be able to escape during the process he is reviving.
