Sega would headhunt and threaten developers from joining their competitors and got the yakuza involved.
Actually the Yakuza ones are more arcade wars than console wars.
Console war was indeed happened in US but in Japan for SEGA's more like arcade wars since Mega Drive has no chance in beating Sufami's dominance anyway.
SEGA's competitor were NAMCO, SNK, and Konami in arcade business, not Nintendo.
And arcade centers' back then aren't a family-friendly places like right now, so no wonder if its handling of business was kinda shaddy.
For console business, Nintendo's actually the one who's threatened other developers from making games from their competitors.
Most SEGA exclusive games were only from SEGA themself and third party games from SEGA usually also available in other consoles.
If SEGA's involving Yakuza, most likely it's arcade business.
SEGA's threatened arcade centers who prioritizes other arcade games more than ones for them.
SEGA's dominance in arcade business let them have monopolize hundreds of arcade centers in Japan, even around 1,000 arcade centers in the late '90s.