"They say we're too young to amount to anything else, but look around. We worked too damn hard for this to just give up now." What literary term would that be?
This opening line from the song "She Looks so Perfect" by the band, 5 Seconds of Summer, when taken out of context does not appear to present any obvious literary device. However, if you look at the context of the entire song, as well as the context of the speaker (here the lead singer), you could consider this line to be ironic.
First, the speaker is very young, in his early 20s. By almost any standard of age and life-experience, this speaker has not reached an age where he would be considered "wise," or even particularly well experienced in life. The opening line admits this with "They say we're too young to amount to anything else." At face value, this is commonly accepted by older adults as true.
But then he argues with this point by suggesting that in this relationship, the two people involved have worked "too damn hard to give up now." From an older and more experienced adult perspective, it is difficult to define a young 20-something love relationship as something that includes a great amount of difficulty. Therefore, this line could be considered situational irony. It is almost like these are meant to be words of experience and wisdom, coming from the mouth of a young person who lacks both.
Finally, and a bit more simply, given that the rest of the song seems to outline a story of a breakup, this line could also be considered foreshadowing.