何(なん)と言(い)ってもBy any account, All the same, No doubt

どうせ expresses resignation or pessimism about an inevitable outcome, often with a negative tone, as in どうせ失敗するから (It’s bound to fail anyway). In contrast, 何といっても emphasizes something’s outstanding or most important quality, as in 何といっても彼が一番だ (No matter what you say, he’s the best). The former carries a defeatist tone, while the latter asserts something positively.

Both phrases assert something strongly, but from different angles. ～というのは事実だ affirms something as a literal fact, e.g. 負けたというのは事実だ ('It's a fact that we lost'). 何といっても expresses what the speaker feels is most important, e.g. 何といっても家族が大事だ ('No matter what you say, family is important').

Both highlight priority or importance. 何より stresses value or priority, as in 健康が何より大切だ (Health is more important than anything). 何といっても emphasizes undeniability or decisiveness, as in 何といっても彼が一番だ (No matter what, he’s the best).3

Both can mean after all, but differ in nuance. 何といっても emphasizes the decisive point, as in 何といっても経験が大事だ (Above all, experience matters). 何しろ introduces a reason or background explanation, as in 忙しいんです。何しろ締め切りが近い (I’m busy, after all the deadline is near).