One of the most dangerous chess variants, for me, is 960. The reason is quite simple: it fundamentally breaks with everything we usually know about traditional chess, relegating opening theory to the background and forcing us to rely almost exclusively on creativity, intuition, and the ability to adapt immediately.
In classical chess, many players study opening lines for years, whether they memorize them or not, and rely on that preparation to reach secure positions in the middlegame. Even amateurs often have their "usual defenses" and initial move patterns that allow them to feel comfortable on the board.
But in Chess 960, that security vanishes, because at the beginning of each game, the pieces on the front rank are placed randomly, respecting only two rules: the bishops must be on squares of opposite colors and the king must be between the rooks so that castling is still possible. The result is 960 different possible starting positions.
This makes it a dangerous variation because it completely disarms those who rely on memory instead of understanding. Theory is reduced to zero on the first move, and suddenly a grandmaster and an amateur have to face much wilder terrain.
Each game is like a journey into the unknown
Another aspect that makes it dangerous is that, since there is no "established manual" for each position, mistakes appear more quickly. In traditional chess, making an inaccuracy in the opening can go unnoticed for ten or fifteen moves, because the opponent also usually follows known patterns.
But in 960, a single weak move can open unexpected lines for the opponent and leave you lost in just a few minutes. Adaptation, immediate evaluation, and mental flexibility become more decisive weapons than ever.