The following game illustrates what happens if White tries to grab a pawn in Larsen's Opening with 6.fxe5 fxe5 7.Bxc6+? bxc6 8.Bxe5?? Black wins by force. Instead, White should play 6.Qh5+ g6 7.Qh4 exf4 8.exf4 Bd7 9.Nf3 Nb4 10.Bxd7+ Qxd7 11.Na3 O-O-O or 6.fxe5 fxe5 7.Nf3 Bg4 8.h3 Bxf3 9.Qxf3 Nf6 10.Nc3 a6, in either case with approximate equality. Note that in the game continuation, 14...Bf5!, staying in the middlegame, was even better than allowing White to go into a lost endgame.
Note also that 10...Qxh1!, as played, was much better the tempting 10...Bg4?! I think that I once had the White side of this many years ago against James Fagan in a blitz tournament at the Elbo Room. White survives after 11.Nc3!, and now (a) 11...Qg6 12.Bxh8! Bxd1 13.Nxd1!, when White is only a little worse, or (b) 11...Qxh1 12.Qxg4 Qxg1+ 13.Ke2 Qxa1 14.Nxd5 Qh1 15.Qe6+ Be7 [15...Kd8 16.Nf6 (16.Bf6+ also draws) 16...Qg2+ 17.Kd3 Qf1+ 18.Ke4 Qh1+ 19.Kd3 with a draw by perpetual check] 16.Nxc7+ Kd8 17.Nxa8.
ADDENDUM: White can also grab the pawn immediately on move 7 without first playing Bxc6+. It turns out that this is a better try, although still weak. After 7.Bxe5 Qh4+ 8.g3 Qe4 9.Bxg7 Qxh1 10.Qh5+ Ke7 11.Qh4+ Kf7 12.Bxh8 Qxg1+ 13.Bf1 Bf5 14.Nc3 Nge7 15.Ne2 Qh1 16.Bc3 Ne5 17.O-O-O Qe4 18.Qxe4 dxe4 Black is up a piece for two pawns. The alternative 11.Kf1 is clearly winning for Black after 11...Be6 12.Be2 Be5 13.Bxh8 [or 13.Bxe5 Nxe5 14.Qxe5 Rf8+ 15.Bf3 Rxf3+ 16.Ke2 Qxg1 17.Qxc7+ (17.Nc3 Qg2+ 18.Kd3 Nf6) 17... Kf6] 13...Rf8+ 14.Bf3 Bxh8.
