If Caruana and Aronian draw, it's a 4-way tie, and Kramnik wins the tiebreak with the only winning record in games played against the other three players involved in the tie (the "Direct" column in the charts below).
If Aronian beats Caruana, it's a 5-way tie, and all five tied players will have an overall even score in games played against the other four. The tiebreak goes to most wins (fewest draws), and Kramnik wins that easily with 5 wins.
Following is the list of combinations resulting in Kramnik winning, with the 8-letter string indicating the results of the following respective games: (D=Draw W=White wins B=Black wins)
Mamedyarov must beat Grischuk Ding Liren must lose to Kramnik So must beat Karjakin Caruana must not beat Aronian Grischuk must beat Caruana Aronian So Karjakin must lose to Ding Liren Kramnik must beat Mamedyarov Score Direct Wins S-B WBWDWDBW 1 Kramnik 7.5 /14 4.0 / 8 5 50.00 2 Mamedyarov 7.5 /14 4.0 / 8 3 52.00 3 Grischuk 7.5 /14 4.0 / 8 3 51.75 4 Caruana 7.5 /14 4.0 / 8 3 50.75 5 DingLiren 7.5 /14 4.0 / 8 2 52.00 6 Karjakin 7.0 /14 0.0 / 0 4 49.00 7 So 6.5 /14 0.0 / 0 2 44.50 8 Aronian 5.0 /14 0.0 / 0 1 36.50 WBWDWWBW 1 Kramnik 7.5 /14 4.0 / 8 5 50.50 2 Mamedyarov 7.5 /14 4.0 / 8 3 52.00 3 Grischuk 7.5 /14 4.0 / 8 3 51.50 4 Caruana 7.5 /14 4.0 / 8 3 50.75 5 DingLiren 7.5 /14 4.0 / 8 2 52.00 6 Karjakin 7.0 /14 0.0 / 0 4 49.00 7 So 6.0 /14 0.0 / 0 2 42.50 8 Aronian 5.5 /14 0.0 / 0 2 39.25 WBWDWBBW 1 Kramnik 7.5 /14 4.0 / 8 5 49.50 2 Mamedyarov 7.5 /14 4.0 / 8 3 52.00 3 Grischuk 7.5 /14 4.0 / 8 3 52.00 4 Caruana 7.5 /14 4.0 / 8 3 50.75 5 DingLiren 7.5 /14 4.0 / 8 2 52.00 6 Karjakin 7.0 /14 1.0 / 2 4 49.00 7 So 7.0 /14 1.0 / 2 3 46.00 8 Aronian 4.5 /14 0.0 / 0 1 33.25 WBWBWDBW 1 Kramnik 7.5 /14 3.5 / 6 5 50.75 2 Mamedyarov 7.5 /14 3.0 / 6 3 52.00 3 DingLiren 7.5 /14 3.0 / 6 2 52.00 4 Grischuk 7.5 /14 2.5 / 6 3 51.50 5 Karjakin 7.0 /14 1.5 / 2 4 48.75 6 Caruana 7.0 /14 0.5 / 2 3 48.75 7 So 6.5 /14 0.0 / 0 2 45.00 8 Aronian 5.5 /14 0.0 / 0 2 39.75 WBWBWWBW 1 Kramnik 7.5 /14 3.5 / 6 5 51.25 2 Mamedyarov 7.5 /14 3.0 / 6 3 52.00 3 DingLiren 7.5 /14 3.0 / 6 2 52.00 4 Grischuk 7.5 /14 2.5 / 6 3 51.25 5 Karjakin 7.0 /14 1.5 / 2 4 48.75 6 Caruana 7.0 /14 0.5 / 2 3 48.50 7 Aronian 6.0 /14 1.0 / 2 3 42.50 8 So 6.0 /14 1.0 / 2 2 42.75 WBWBWBBW 1 Kramnik 7.5 /14 3.5 / 6 5 50.25 2 Mamedyarov 7.5 /14 3.0 / 6 3 52.00 3 DingLiren 7.5 /14 3.0 / 6 2 52.00 4 Grischuk 7.5 /14 2.5 / 6 3 51.75 5 Karjakin 7.0 /14 2.5 / 4 4 48.75 6 Caruana 7.0 /14 2.0 / 4 3 49.00 7 So 7.0 /14 1.5 / 4 3 46.75 8 Aronian 5.0 /14 0.0 / 0 2 36.50