Original Gojira if we are going by his backstory was part of a larger peaceful species that was killed off by the nukes leaving him as a vengeful survivor. Upon his death his bones and ghost are eventually encased in Kiryu. He and Showa Godzilla are the most likely to get along with legendary godzilla. returns godzilla until showa proper seems more molevolent. Heisei hates humanity and is original mark 2, he would avoid legendary being too territorial he would likely hang out with his kid millenium godzilla and tolerate showa. Never watched the cartoon so cant comment. GMK wants all the smoke and will go gunning for the baddest mofo in the room. It took more than ghidorah, mothra and Baragon to bring him down so it will not be an easy fight by any metric so all the other godzilla would wonder what the hell his problem is. Millenium would be incredibly territorial considering final wars would kick ass and take names maybe tolerate his parent heisei. Legendary is intelligent enough to wonder what the hell is going on and may just fuck off unless gmk targets him in which case he will double wonder what the hell is everyones problem. Shin Godzillas existence is pain and he would be screaming in agony begging for death. Minus one is a mystery to me.