Amazing Spider-Man #798 (available on eBay) is out tomorrow. Without a doubt this is a full first appearance of Red Goblin. He appears on several pages with dialogue and is named. Originally it seemed like he would appear this issue and the identity would be shown in #799, nope, it is all here.
Spoiled images are redacted. The accompanying text is not. Proceed only if you are ok with spoilers.
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Amazing Spider-Man #798 (available on eBay) starts like many previous issues, with Green Goblin attacking.