El error indica que private Lawyer lawyer debe ser una colección, ya que es un @OneToMany relación. En el Country clase, la última relación debe ser
@OneToMany(targetEntity = Lawyer.class, cascade = { CascadeType.ALL }, orphanRemoval = true)
@JoinTable(name = "lawyer_cscd", joinColumns = {
@JoinColumn(name = "country_code", referencedColumnName = "country_code") }, inverseJoinColumns = {
@JoinColumn(name = "lawyer_batch_no", referencedColumnName = "lawyer_batch_no") })
private Set<Lawyer> lawyer;
// or a Collection/List/etc.
