要比较两个Json集合并返回修改后的值，可以使用以下步骤：

1. 导入所需的库：json和deepdiff。

import json
from deepdiff import DeepDiff

2. 定义两个Json集合：

json1 = '''
{
  "name": "John",
  "age": 30,
  "city": "New York"
}
'''

json2 = '''
{
  "name": "John",
  "age": 35,
  "city": "Los Angeles"
}
'''

3. 将Json转换为Python对象：

dict1 = json.loads(json1)
dict2 = json.loads(json2)

4. 使用DeepDiff比较两个字典对象的差异：

diff = DeepDiff(dict1, dict2, ignore_order=True)

5. 检查差异的类型，如果差异是值的修改，获取修改后的值：

if 'values_changed' in diff:
    for change in diff['values_changed']:
        modified_value = change['new_value']
        print("修改后的值：", modified_value)

完整的代码示例：

import json
from deepdiff import DeepDiff

json1 = '''
{
  "name": "John",
  "age": 30,
  "city": "New York"
}
'''

json2 = '''
{
  "name": "John",
  "age": 35,
  "city": "Los Angeles"
}
'''

dict1 = json.loads(json1)
dict2 = json.loads(json2)

diff = DeepDiff(dict1, dict2, ignore_order=True)

if 'values_changed' in diff:
    for change in diff['values_changed']:
        modified_value = change['new_value']
        print("修改后的值：", modified_value)

这样就可以比较两个Json集合并返回修改后的值了。