This should be a simple repair is you're a DIY kind of person. If you're not experienced with electronics, specifically Li-ion batteries and the corollary precautions, get yourself all learne up first.

I suggest looking at iFixit, they may even have a guide for TranzX batteries. Your next resource would be Grin Technologies (https://ebikes.ca/).

Odd corrosion for what I assume is copper? Could be that it got splashed with something acidic, but if I were a guessing guy it's from a loose/improper grounding connection to the terminal. Loose grounding increases resistance and will start to cause aggressive pitting on the terminal.

Depending on the battery company, a loose grounding wire may be covered under warranty. A battery meant for transportation should be expected to hold up to vibrations and activity that normally knocks wiring around.

If not replacing a terminal should be pretty easy even if you have to make one yourself, but make sure to look up a diagram of the battery and make sure you wired it correctly.

maybe there is a loose connection? You could take it apart and look with a multimeter if everything is connected at the battery cells? I am german and there is actually a forum: pedelecforum.de where a bunch of people have a problem but i did not found something related to yours. Maybe you can specify your problem more then I can search once more, but first i would take a look if there is a loose connection.

this is just my local shop example part: https://ebikes.ca/ebike-parts/battery-stuff/battery-accessories/con-dt-5pin.html

you will probably want to find whatever shop it most convenient for you, and get the piece with the same number of contacts.

you might also be able to bridge unused pins on the battery and battery receiver. I wired mine which is 6 pin to be 3 + and 3 - to not have this failure from just one pin damage. Most I have disassembled the extra pins are not connected and it just uses the outer two as single + and -.

It could be corrosion, but none of the nearby contacts are affected. If the battery got splashed, odds are the other contacts may have also gotten some. But they all look ok. Given how extreme it is, I'd consider arcing, which could involve bad grounding or shorting somewhere. It's hard to see if the plastic around it has been damaged or not. If yes, then it's definitely some sort of spark.

Replacing the contact should be fairly easy if you can get the part. But you might want to go upstream and check the individual cells and contacts. Many of these batteries are clusters of 18650 cells. Easy to swap out. If there is any sign of damage to the internal battery contacts, then you might want to replace the contacts AND the cells.

Simple soldering ($20 soldering pen and material) and a wire brush. $30 multimeter to check for continuity and voltage/current levels.

My buddy had to replace the contacts on his battery and ebike this past spring after he absolutely ruined his contacts with snow and gunk. He was able to make due initially with dielectric grease and a contact cleaning but eventually he jiggled too hard on a bump and sparked the contacts. Let me ask if he repaired his battery or replaced it. He had a stock Aventon Level 2 battery from 202...1?