Bump, clash, collide, conflict are comparable when they mean to come or cause to come into violent contact or close or direct opposition.
Bump is used primarily of physical matters and then implies a forceful knocking or running against, typically with thudding impact.
It may also suggest encountering an obstacle or difficulty.
Clash may suggest hitting, knocking, or dashing together or against with sharp force and jangling metallic din or sharp, although sometimes short-lived, variance, incompatibility, or opposition.
Collide denotes a more or less direct running together or against with a definite and often destructive force or shock or it may indicate a forceful direct disagreement or opposition.
Conflict is archaic in senses involving physical contact and is used to convey the notion of variance, incompatibility, or opposition.