Why does Natsu always need to power-up in order to win a fight? Is anger his only way to get strong?

I think its more of the case where he is usually unable to draw out the full extent of his base powers normally but ends up doing it over the course of the fight, that is why he seems to lose initially then ends up winning, but the issue of always needing to power up to win a fight is untrue, the anger power-up has only happened a few times if u count the erigor thing, and that one wasn't a power up, just simple relationship between Temperature and pressure. To be fair i only remember the anger stuff in the daphne arc, i'll like you to least the occasions you are talking about. Remember Laxus is not included as it wasn't an anger thing that caused him to win, laxus had taken in so many hits, duelled mystogan, erza a little, natsu and gajeel plus doing so many high level magic, including fairy law and thunder palace, plus he was still kicking natsu's ass before the halbred, then Plot no Justu kicked in an natsu wins, check the wiki, laxus is described at that point as Internally and externally weakened. Apart from those event tell me the situations where natsu uses anger to power-up, cos i can't remember at the moment

Dragon Slayer Magic has Many skills such as The dragon roar,etc... And the question u ask about is natsu get angry he will win the battle. The answer is no. The anger of Natsu is not
getting mad. Its a technique call Flames of emotions. When he gets anger or emotioned, He will enter this mods and Boost up his Power

because he ain't strong enough to defeat some opponents. against jellal he needed df and luck (jellal wasnt able to execute abyss break); vs zero he needed df again because zero was much stronger than him; and against hades he neede lfd because hades was a god and he needed to be defeated. i think its sometimes stupid because he never trains but gets power ups from nowhere i think its called plot induced shit