にとって

"For X; from X's standpoint." Marks the person or group from whose point of view something is judged. It is usually followed by an evaluation such as importance, difficulty, or necessity.

Common in both speech and writing to say how something matters to or affects someone. It is typically followed by evaluative predicates such as 大切だ, 難しい, 必要だ, or チャンスだ. It can also frame a judgment within an opinion (私にとっては、この案が一番いいと思います). Unlike に対して, it does not mark the target of an action. Unlike としては, it does not itself introduce someone's stance.

• 1.
  に対してN3「に対して」marks the target of an action, attitude, or feeling (e.g., 「先生に対して失礼だ」), and also has contrast and proportion uses; 「にとって」evaluates meaning or value from a subject's standpoint, so the two are not interchangeable.
• 2.
  としてN3「として」expresses acting in a certain role, capacity, or position, or treating something as having a certain use or name, and is followed by actions, obligations, or judgments—it does not make an 'for...' evaluation. When stating your opinion, say 「私としては賛成だ」, not 「にとって」.
• 3.
  からすると / からすればN2「からすると」also has an inference use ('judging from...') that 「にとって」lacks. When both express a standpoint they are close, but 「からすると」focuses on how the person in that position sees things, while 「にとって」focuses on what meaning or value something has for them.
• 4.
  にしたらN2「にしたら」emphasizes putting yourself in the person's shoes to imagine their feelings or thoughts, often implying a view different from others', and when talking about others it often pairs with 「だろう」; 「にとって」focuses on evaluating what something means to the subject. When the second clause is an evaluation, the two are often interchangeable.
• 5.
  としてはN2「としては」, when expressing a standpoint, is followed by opinions, attitudes, or wishes, as in 「私としては賛成です」, where 「にとって」cannot be used; it can also evaluate against a role or category as a standard, as in 「新人としては上出来だ」, a use 「にとって」does not have.
• 6.
  から見るとN2「から見ると」makes guesses based on something, or evaluates from someone's viewpoint, often pairing with 「らしい」or 「だろう」; 「にとって」only states what something means to a subject or its benefits/harms, and does not express conjecture, so the two are generally not interchangeable.

に対して marks the target of an action or attitude, and として marks a role or capacity ("as"), whereas にとって marks whose standpoint an evaluation is made from. からすると/からすれば, から見ると, and にしたら also express a viewpoint but tend to present a judgment reasoned or imagined from that position (にしたら especially for another person's feelings), while としては introduces someone's position or opinion; にとって simply states how something is valued by or affects someone.