controller.js

function loadPkmn(start, end) {
  for (var i = start; i <= end; i++) {
    $http.get('https://pokeapi.co/api/v2/pokemon/' + i).then(function(res) {
      $scope.$apply(function() {
        $scope.kantoPkmn.push(res.data);
      });
    })
  }
}

loadPkmn(kanto.start, kanto.end);

service.js

.service('pkmnService', ['$http', '$q', function($http, $q) {
    var deferObject,
    pkmnMethods = {

      getPromise: function(start, end) {
        var promises = [];
        var deferObject  =  deferObject || $q.defer();
        for(var i = start; i <= end; i++) {
        	var promise = $http.get('https://pokeapi.co/api/v2/pokemon/' + i);
        	promises.push(promise);
        }

        $q.all(promises).then(function(values) {

        });
        return deferObject.promise;
      }

      // getPromise: function() {
      //   var promise = $http.get('https://pokeapi.co/api/v2/pokemon/'),
      //   deferObject  =  deferObject || $q.defer();
      //   promise.then(
      //   // OnSuccess function
      //   function(answer){
      //     deferObject.resolve(answer);
      //   },
      //   function(reason){
      //     deferObject.reject(reason);
      //   });
      //   return deferObject.promise;
      // }
    };

    return pkmnMethods;
  }]);