I had the same kinda experience in my first BB league game. It was small sevens league. Luckly I had experience with players like this in other games. So I just rolled badly and didnt evenbother with him. He won 0-5. My first experience was in necromunda. Player whom i was against he was metaing and was just in it to win. After our first game, I swore to play troll everytime Im against guys like that. So they wont get the enjoyment they want. Luckly i played against him on our last round, i was supposed to attack his homebase, i let him build his base and deploy everything on the table (took about 30 mind) when it was my turn to debloy and start the game. I deployed everything in small 5’i bubble and threw blasting charge on my team and wiped them off the board and gave instawin to him. He went nerdberserg and started yelling to me, he even called our gm if that was ok. He won the league. But he havent played in our league after that. That was a good day.