Bob Reynolds the Sentry/Void is a single entity, a confused mind struggling against itself. He/they didn't wanna die bad enough inside the sun, this is portrayed in the dialogue as the sentry persona arguing with the void persona. By the end of siege he/they were no longer lingering and wanted to die bad enough to stay dead - it's not the damage that put him down for good, it's the fact he chose not to reform - this, in turn, is shown through dialogue and art as both the Sentry and Void forms saying "kill me" one immediatelly after the other. If a man commits suicide by cop, it's still suicide. Bob commited suicide by Thor, so the plot was wrapped up as a battle and a win for Thor instead of bob going back to the sun to trying and kill himself again. If he wanted to reform he would have.
This wasn't the first time the line between their seemingly separate personalities disappeared either: the void, contrary to what one might expect, wanted to kill bullseye upon hearing his wife was dead. Bob still responds as a single being when the stimulus is sufficient and he is not conflicted about it.
Bob Reynolds finally wanted to die bad enough to stay dead and this is, in fact, solid character development: his wife was dead, his last anchoring to this world was gone, he no longer knew what he was, he couldn't run from his character flaws or his past anymore. He had enough.