After a scientific accident that leaves everyone dead and one with fire abilities, the survivor must travel to a sacred temple to learn how to control his abilities.

As Nir points out, your latest attempt is closer,

However, your description of your characters is vague.

You describe your lead character as 'someone' and you describe the antagonist as ' another' ... this really tells us nothing. You can give us a brief description without actually adding too many extra words to the logline. Here would be an example:

"When an accident leaves a nerdy student with the ability to manipulate fire. He must race to an ancient temple while avoiding a ruthless cult that wishes to use his abilities to awaken a long-dormant fire god."

The last version is the clearest so far, the wording you were using before was confusing. The problem is that his goal isn't clearly motivated, who is threatening to take hold of what? His ability? The temple? Fire?

After a devastating accident leaves someone with the ability to manipulate fire, the man goes to an ancient temple to learn how to control it before someone else takes ahold of it, using it for darker purposes.