Short answer: you are facing Pokemon that are optimised for competitive battles - if this is a Blaziken that hasn't been raised specifically for this, then it is at a disadvantage right from the beginning.
This is because you are facing Pokemon built for competitive battles. Players EV train and IV breed their Pokemon for these battles, so if you haven't done this for your Blaziken, that puts it at a natural disadvantage. Here are what Blaziken's stats would look like at level 82 if it were to have a Jolly nature, perfect IVs and EVs of 252 Atk, 252 Spd and 4 HP (the optimal competitive battling spread):
Special Attack: 189
Special Defence: 145
This Blaziken has similar defensive stats and HP to yours, yet it uses no investment in those stats besides the perfect IVs. This proves that a. your Blaziken does not have perfect IVs and b. your Blaziken's EVs are randomised as there'd have to be EVs in those stats to make up for imperfect IVs. This is bad because you'd have to leave out EVs for Attack and Speed (Blaziken's two most important stats) to be able to have defensive stats like that. This and your Blaziken's imperfect IVs explain why it deals less damage. Blaziken's inability to take hits can be traced back to the Pokemon's natural frailty, which you really can't do much about.
What stats did you Super Train exactly? If you randomly alternated between each one, then that explains your randomised EVs, as Super Training directly affects EVs. The random EVs can also be explained by use in completing the main game - if this is the Blaziken you used to pass the game's story, this is most likely the case as well. As stated before, randomised EVs are bad because it means you can't focus on the stats the Pokemon needs most. Blaziken is naturally frail so it isn't worth putting EVs in defensive stats when you can put them in offensive stats to deal more damage.
If you have a Reset Bag in Super Training, you can delete Blaziken's EVs and start over, aiming for EVs that maximise Attack and Speed, which are the most important stats for Blaziken. IVs are much more difficult to control because it is impossible to change them, which means they require many hour's worth of breeding to finally get a Pokemon with perfect IVs.
Showdown teambuilder used to determine stats
Article on EVs (Effort Values)
Article on IVs (Individual Values)